An Outline of Non-Violent Games in History

After a brief look at the history, objectively non-violent video games appear to have started out with main frame computer re-creations of traditional games like Nim or Chess, then transitioning to arcade-styled sports games like "Tennis for Two" and "Pong," and eventually to simulation games, followed by games that became increasingly immersive and story-based, such as the PC adventure genre.
As games became increasingly sophisticated, the genres were increasingly blended in various ways. Eventually, the RPG and "stealth" variations of the action genre started featuring the option to solve conflicts without using violence in an increasing number of titles. Last but not least, the rise of "casual games" led to a rebirth of the adventure genre, re-incorporating the DOS-era traditions of unique artwork with straight-forward point-and-click interfaces, as well as non-violent strategy games featuring storylines comparable in some cases to those found in RPGs. Developments are still continuing, but at the moment the future of completely non-violent games is looking bright.

Non-Violent Arcade Games
While many games had been developed for expensive main frame computers as early as the 1950s, mainstream gaming markets were initially dominated by arcade games, since technology had not yet advanced to the point where home computers and consoles could be manufactured profitably. Arcade games competed vigorously with the pinball machine industry in the US, and arcade games usually revolved around real-time action that demanded fast reflexes (and the continual pumping of quarters into the machine). Some featured shootouts between space ships or arguably "harmless" action like that seen in Pac-Man, but arcade machines also had a number of completely non-violent titles:
Taito flyer for Japanese edition of Speed Race, an innovative arcade racing game.
In the 1970s, prolific game engineer Tomohiro Nishikado developed an impressive number of groundbreaking arcade games in a short period of time for the Taito company, including 1974's  "Speed Race," a vertically scrolling racing game machine complete with custom steering wheel, gear-shift, speedometer and tachometer. Like most of his games, his racing concepts were influential and were later copied by many other arcade and console designers. (On the other side of the coin, however, he also developed "Western Gun" in 1975, a western-themed shooting game which has been cited as the first game to feature mortal combat between two human gunslingers.)
Midway flyer for U.S. release of "Gun Fight," aka "Western Gun" in Japan.
Later in 1979, the fore-runner of what later became known as the "Stealth" genre appeared on the arcade scene through Hiroshi Suzuki's Manbiki Shounen (Shoplifting Boy) , in which the objective was to steal "$" symbols from a shop without being spotted by the owner—or else "shoplifting boy" would be hauled away by the police, and the player would have to insert another coin of their own, if they wanted to play again. While outnumbered substantially by action titles, a handful of stealth genre games continued being developed through the 1980s onward, eventually finding popular acclaim through the Metal Gear and Thief series (among others), and eventually evolving to enable the possibility of winning without using violence.
The 1987 release of the first Metal Gear game on the MSX2 was a landmark "stealth" title, even if violence was a central theme of the game.

Non-Violent Computer Simulations, Adventures, and RPGs

The 1971 simulation "The Oregon Trail" was one of the earliest predecessors to later genres of games including simulations, RPGs, and adventures. While not devoid of death or violence (since it provided the option to hunt wild beasts for food, for example), the emphasis was on intelligent planning and surviving the journey over the Oregon Trail, rather than on Wild Western shoot-em-up action or other forms of violent gameplay.
The popular simulation Oregon Trail was a simulation with RPG elements and a primarily non-violent objective.
Another highly influential game was text-based game "Colossal Cave Adventure" in 1976, focusing on exploration, treasure-hunting, and adventure. The evocative text in Adventure's introduction read: "Somewhere nearby is Colossal Cave, where others have found fortunes in treasure and gold, though it is rumored that some who enter are never seen again. Magic is said to work in the cave..."
The game required the player to use text commands to navigate through the cave and collect as much treasure as possible, and then escape from the caverns alive. By some accounts, this game later inspired Roberta Williams to create adventure games beginning with "Mystery House," and later 1980's "King's Quest," which became a successful series with many sequels, and was highly influential on future generations of adventurer game designers.
One of many fairy-tale scenes from AGD Interactive's updated graphical version of the original King's Quest
King's Quest was not devoid of violence—as Sir Graham had several dangerous encounters obliging him to dispatch an evil witch, giant, and dragon—but these fairy tale encounters were dealt with quickly, while the majority of the game was focused on non-violent exploration and puzzle-solving. The game inspired many other series of adventure games with minimal emphasis on violence, including newer generations of adventure games such as the Awakening series, some of which are completely devoid of violence.

The phenomenon of the CRPG ("computer role-playing game") developed in the same period, inspired in significant part by the 1974 release of the first edition of "Dungeons and Dragons." Unlike adventure games, CRPGs have typically always mandated a much larger number of combat encounters, partly because battling monsters or foes was part of a legendary medieval-fantasy setting, but partly also since early technical limitations forced developers to keep their game engines reasonably simple, making it difficult to provide a wide range of options for getting past the types of monsters typically encountered in "dungeon crawl" genre RPGs. In later generations of CRPGs, the option to be able to win the games with the option of avoiding violence and killing started to appear, but was mostly absent from the earliest "dungeon crawls."
An early edition of a D&D "Dungeon Master's Guide," in which battles were commonplace.
Below the Root (released in 1984) was one of the notable non-violent adventure games with RPG elements, but no easily definable genre. Below the Root stood out from the crowd for being unique in a number of ways, including its absence of violence. The game takes place in a unique fantasy world called Green-sky, where a utopian society living in the trees and abiding by a strict code of conduct has been shaken by the discovery that less utopian race of beings lives in caverns beneath the forest.
Cover of the novel Below the Root by Zilpha Keatley Snyder, upon which the 1984 non-violent computer game was based.
In the game, the player must assume the role of one of the characters from the books (written by Zilpha Keatley Snyder, who cooperated with the game designers and artists while the game was being developed) in an attempt to save the realm. For the most part, "violence" only occurs when the player is injured by accidentally falling out of the trees, by colliding with a few dangerous tree creatures, or by becoming imprisoned— but in each case the worst outcome is to become unconscious, then re-awakened in a "nid-place" elsewhere in Green-sky.

Another notable non-violent offering appeared in 1988 when Cyan software (created by brothers Rand and Robyn Miller who later created Myst) created "The Manhole," a non-violent fantasy exploration game aimed at children, built on a similar point-and-click interface that was later used in Myst.
Cover of a later CD-ROM Masterpiece Edition of Cyan's The Manhole
Another non-violent landmark in gaming history appeared in 1989, when the creators of SimCity finally managed to convince distributors to support their now-legendary game, despite its deviation from the prevailing norm in computer games. SimCity was a non-violent and open-ended simulator with an unusual premise: The goal of the game was to start with an undeveloped patch of land, and then build a thriving city, striving to balance the need to keep the citizens happy and prosperous with the need to optimize revenues.

Non-Violent Casual Gaming Starts Growing

Educational software aimed at children was produced during the growth of the PC gaming market also, but otherwise non-violent titles can be rather hard to find in the timeline of higher-profile commercial games. An exception, of course, were the various "casual" games that were always available, even if no particular release stood out from the pack. Various non-violent computerized strategy and board-game reproductions of famous games like Nim, Chess, and various card games had been released ever since the very earliest days that computer games were developed. One noteworthy new and original entry was Tetris, which was created in the early 1980s by Alexey Pajitnov (a mathematician and AI researcher working behind the Iron Curtain), and ported to IBM-PC by his colleagues. Tetris was highly popular and ended up bundled with Nintendo's first Game Boy in 1989.
1988 IBM-PC cover art of Tetris, released as "Tetris: The Soviet Challenge" by Spectrum Holobyte.
In 1990, Microsoft made another move that had a big impact on the future of casual gaming, when they included a computerized Solitaire game as free software bundled with the new Windows operating system. This resulted in large numbers of former "non-gamers" who had never had any prior interest in gaming suddenly starting to play "casual games," finding they enjoyed computerized gaming more than expected.

Non-Violent Landmarks of the 1990s

In many respects, the early 1990's were a bigger decade for violent gaming than non-violent ones, as real-time war strategy games and first-person shooters became wildly popular and successful. However, a few honorable mentions were also released in the early 1990s, contributing to the popularity of non-violent action and racing games:
In-game screenshot from the SNES classic Super Mario Kart, featuring popular characters from the Mario universe.
One was Nintendo's new racing game Super Mario Kart, the first of a highly popular and influential series on many systems, and involving little "violence" other than an array of friendly characters competing with actions such as bopping each other's go-karts with turtle shells.The previous year had also seen the release of Sonic the Hedgehog, spurring the popularity of the Sega Genesis system.
Sonic the Hedgehog
Sonic arguably deserved special honors as a non-violent "action" game, since every robot he busted into a cloud of sparks and smoke released a small friendly animal that had been imprisoned within by Doctor Robotnik, and even Robotnik himself never met with lasting injury after each of his schemes was foiled. However, Sega's other ported releases aroused controversy.  In 1993, Sega releases including Mortal Kombat spurred Senate hearings resulting in the imposition of a rating system on console video games, while the notorious 1st-person shooter Doom made its debut on the PC in the same year.
Cover art for the 1993 PC game Myst by Cyan, Inc.
One of non-violent gaming's bigger milestones appeared when Cyan released Myst in 1993, absorbing a huge number of players with its pre-rendered high-definition graphics, rich atmospheres, and mysterious plotline, which only gradually unfolds during extensive non-linear exploration and puzzle-solving in the in-game world. Myst surprised many people by being a huge success that set records in PC game sales for years to come, despite having a much simpler game engine and a total absence of violent gameplay.
Exploring the mysterious island in Myst
While not usually considered a "casual" game due to its high difficulty and depth, Myst actually used a straightforward point-and-click interface to navigate through mostly still images with partial animations in some areas. This formula was used very successfully in dozens of other graphically rich adventure games that later appeared in the rebirth of the adventure genre through the "casual" gaming marketplace.

Another non-violent gaming development that took place in the 1990s, in part because of the expanded CD-ROM capabilities of systems like the Sony Playstation, was the rise in popularity of music games like the "beatmania" and "Dance Dance Revolution" series. The PS1 was also the host to a large number of racing and sports games, many of which were also non-violent and still commercially successful.

Non-Violent Developments in RPGs & Stealth Games

Console RPG games had been enjoying a golden age in the 1990s, and titles like Final Fantasy IV, Final Fantasy VI, and Chrono Trigger are still considered timeless classics by many RPG fans. Strictly speaking, none of these RPGs could be called "non-violent" since they all involved large amounts of mandatory combat encounters that they player could not avoid.
Three blue imps surround the hero of Chrono Trigger, initiating a combat encounter.
However, an unusual RPG called "Harvest Moon" was also released in Japan in 1996, in which the objective was to restore and maintain an old farm, engaging in non-violent tasks like foraging, farming, and tending animals— and later even allowing the player to court and marry one of a number of young ladies.
Harvest Moon, one of the few console RPGs to avoid combat themes.
In more recent years, the Harvest Moon series (which has been renamed "Story of the Seasons") was very influential on the popular Chinese social game "Happy Farm," which in turn influenced the record-setting Facebook game Farmville, and a large number of similar non-violent farming games designed for mobile devices and the PC casual games market.

1998 was also an important year for the stealth genre, with the release of both "Metal Gear Solid," and "Thief: The Dark Project." Both were dark games lacking the more warm-hearted and romantic approach of most console RPG games, but both nonetheless widely popularized the stealth game genre in which it was not actually necessary to kill any enemies to win. Future developers of high-profile releases inspired and influenced by these titles began designing more games in which killing could be avoided if "tactical stealth" could be used instead.
Thief: Gold
Non-violent Games in the New Millennium: 

In the year 2000 a new non-violent "life simulation" game called "The Sims" became the best-selling PC game of all time, breaking Myst's long-standing record. In 2001, another big score for popular and profitable non-violent gaming took place with Nintendo's release of "Animal Crossing," an open-ended village simulation featuring a cast of anthropomorphic animals. The game was extremely popular and critically acclaimed.
Nintendo Gamecube box art for Animal Crossing
This was also the case with Mario creator Shigeru Miyamoto's 2005 "Nintendogs," a real-time pet simulator. Arguably, all three games were major entries bridging the gap between "casual gaming" and games with deeper gameplay, since all three were fairly sophisticated, but also open-ended and easy to learn, as well as being non-violent.

As mobile device games bring in over a billion in revenues, the "casual gaming" industry rose in significance, producing a huge number of non-violent games, including a renewal of the point-and-click adventure games that had fallen strongly out of favor with larger commercial developers in the late 1990s. New online distribution platforms and technology made it possible for highly art-intensive adventure games to be produced again using reasonably simple game engines influenced by King's Quest, Myst, and other classic adventure games with a "point-and-click" interface that is easy to learn, and then to sell the games at a fraction of the cost of mainstream titles.
Awakening: Moonfell Wood, one of many completely non-violent adventure games developed since the rebirth of the genre.
In 2006, Nintendo surprised modern console developers by bringing out a new system that actually had lower technical specifications than some of its major competitors, but was intended to attract a much wider audience, capitalizing on the growing trends in "casual" and non-violent games with relatively low learning curves. Some critics expected the system to be a flop for various reasons (ranging from the modest technical specs to the unusual name "Wii" chosen for the system), but the system ended up surprising critics by outselling its competitors and producing a substantial number of best-selling titles that were also notable for having minimal violence: Measured across individual platforms, Nintendo's Wii Sports (bundled with the new system in all regions except Japan) currently holds the #1 spot as best-selling game of all time, followed by Nintendo's NES classic Super Mario Bros., and by another non-violent Nintendo Wii title taking third place: Mario Kart Wii.

In the newer alternative platforms of devices and social media sites, the last years of the decade also saw the releases of Happy Farm, Farmville, and related games influenced directly or indirectly by the non-violent farming-themed RPG Harvest Moon.

Independent & Experimental Nonviolent Games
Box art for the PS3 edition of the independent game Minecraft
Independent game developers also started making their mark with popular releases like Minecraft, an open-ended game based on building lego-like structures, in which a non-violent "peaceful mode" could be selected in order to play without battles. Measured across all genres, Minecraft is currently the #2 best-selling game of all time (one position ahead of Wii Sports), being beaten only by the 1980's classic Tetris. (The achievement is also notable since both Tetris and Wii Sports owe a significant amount of their sales position to having been included as bundled software.)

Independent developers also come up with a growing number of experimental non-violent titles that involved no violence by default. Some have detailed storylines, while others are open-ended experimental projects with little or no plotline or fixed objectives, sometimes being more like interactive "meditations" or interactive art projects.

In the plot-driven genre, some experimental games start defining what some termed as an "exploration" sub-genre of adventure games in which no violence takes place, instead focusing on unfolding of plotlines as player explores and discovers new things. One such game was called "Dear Esther" and released for multiple platforms, involving first-person exploration of a 3d island, without any violence. "Gone Home," released in 2013, is another notable title that is based primarily on exploring an old mansion, with the emphasis on telling a story.
Screenshot from the successful nonviolent game "Flower"
In an even more experimental vein, Flower, released in 2009, was one of a number of games produced by "thatgamecompany," and has been described as a meditative experience in which the player enters the dreams of flowers and controls the wind to blow flower petals through the air.
Journey was another experimental game by the same company, in which the player controls a robed figure exploring a desert landscape while on a journey toward a mountain. It was notable not only for being non-violent, but also for being a multi-player game in which communication with other players takes place without speech or text, using only a musical chime.

Developments for the Future...? 

The commercial success and popularity of even highly unusual non-violent projects has demonstrated that games don't need to be violent to be successful, and that non-violent games can succeed even in genres usually crowded with violent titles.
The Awakening series, one of many series of non-violent adventure games available at Big Fish Games, has been successful enough since its first release in 2010 to result in seven sequels as of 2014.
With non-violent gamers avidly buying non-violent titles even on mainstream systems, and with more rapid growth in areas of the gaming market like mobile and casual games (whose players appear to strongly favor non-violent themes in multiple genres), profitable opportunities probably exist to develop more inherently non-violent games in genres like strategy gaming and RPGs.

Simulations like SimCity have long had some of the deepest gameplay available in non-violent games, but inherently non-violent "epic" strategy games designed on a similar scale and depth as Heroes of Might & Magic or Age of Wonders appear to be very rare— even though the gameplay in turn-based strategy epics could be adapted relatively easily to setting a game in a non-violent context.

The same thing is true of all turn-based RPGs, whose combat systems are already not usually appealing to players that demand "hack-and-slash" or "shoot-'em-up" action, and so could theoretically be adapted fairly easily to feature some type of non-violent substitute for the generic default combat systems.

Modern CRPGs are another interesting prospect: Many of them feature a dangerous and violent game world that nonetheless gives players the option of winning via a "pacifist challenge," which theoretically means they can sell to both violent and non-violent gamers. However, a larger subset of potential CRPG gamers probably also exists who would only want to play the game in the first place in the absence of a violent atmosphere (regardless of whether they are obliged to take violent actions of their own), leaving them free to explore and interact with a less hostile in-game world.