The '00s will be remembered as the decade when the videogame industry got flipped on its head.

Going into the year 2000, the general feeling was that the game industry was ready to put away childish things. The era of Nintendo and kiddie entertainment was over, and the videogames of the future were about multimillion-dollar budgets, mind-blowing photorealism and "digital actors" playing out their parts with human realism thanks to "emotion engines," etc.

Instead, it went down like this: A whole bunch of companies dumped a whole lot of money down the next-gen sinkhole, and the number of publishers that could be counted on to deliver bleeding-edge entertainment without going broke in the process dwindled to just a few.

Meanwhile, many more publishers came to the belated realization that all those simple, accessible games from days gone by weren't obsolete; in fact, there were untold millions of people playing Solitaire on their computers, just waiting for something better to come out.

Our list of the most influential games of the past decade includes, therefore, many games that made big leaps and defined what would come to be traditional aspects of the big-budget grand adventure, and others that pushed the reset button on game design.

Portal (2007) ——————-

This senior thesis cum sleeper hit showed that students could hit it big in the games business – not after years of obscurity but immediately. But the space-bending puzzles of Portal will also have an influence on the way games are sold. Valve could have padded out the four hours of gameplay with extraneous cut scenes or boss battles, but instead it let the game be concise (and a bargain at $20). Portal proved that quality can trump quantity. –Daniel Feit

14. Happy Farm (2008) ———————–

What the hell is Happy Farm, you ask? Why, it's only the Chinese social network farming game that inspired a dozen Facebook clones – the biggest of which, Farmville, has more than 70 million active users. Whether or not social games are the next big thing, Happy Farm's blend of planting, growing and harvesting crops turned out to be the simple game-design formula that had gigantic repercussions. –Chris Kohler

13. Metal Gear Solid 2: Sons of Liberty (2001) ————————————————

This game's winding, twisted narrative was a total mess, but gosh darn it, it stuck its flag in the ground and proclaimed that videogame stories had the right to be twisted messes. Nobody actually knows what the hell happened when Raiden went creeping around Big Shell, but Hideo Kojima was right to suggest by extreme example that action games didn't have to just be about a good guy kicking the asses of generic bad guys. Every videogame story that subverts a player's expectations owes a debt to the ground broken by Metal Gear Solid 2. –Chris Kohler

12. Half-Life 2 (2004) ————————

If Halo is the game of choice for the trigger-happy, Half-Life 2 is the thinking man's shooter, the game that got our brains churning. Puzzles relied on physics, the well-written story wasn't spoon-fed, and the protagonist saw the world through prescription lenses. Half-Life 2 ensured that we'd never think about the first-person shooter in the same way again. –Gus Mastrapa

11. Silent Hill 2 (2001) ————————–

Separating itself from the formulaic, zombie-laden schlock that was beginning to define the horror-game genre, this PlayStation 2 game was grounded in a certain kind of horrific reality. Following the story of the troubled and lost James Sunderland, this psychological horror game exposed the truth behind his relationship with his deceased wife. Silent Hill 2's story tackled taboo subjects like domestic abuse and incest, setting the bar for horror games to come by scaring the player not with hallways full of dessicated monsters but with the horrors found in the hearts of men. –Scott Pierce

10. Metroid Prime (2002) ————————–

Gamers who bemoaned Metroid's rebirth as an FPS took cold comfort in Nintendo's assertion that the game was a first-person adventure, not a shooter. We didn't know what this meant until Metroid Prime dropped. Then it all became clear: It wasn't about gunplay but exploration, puzzle-solving, platforming and story. By breaking the genre free from the clutches of Doom, this GameCube title took one massive stride forward for first-person games. –Chris Kohler

9. Geometry Wars: Retro Evolved (2005) ————————————–

After finding out that the rushed-to-market launch lineup of the Xbox 360 pretty much sucked, early adopters turned en masse to a genre of game that was supposed to have died a decade ago: the arcade-style, high-score shooter. The cheap, download-only Geometry Wars had an addictive learning curve and online leaderboards that turned friends into bitter rivals. It established Xbox Live Arcade as the home of casual games for hard-core players. –Chris Kohler

8. Wii Sports (2006) ———————-

If any one game single-handedly reversed Nintendo's fortunes, this is it. Wii was going to live or die on whether or not consumers bought into the novelty of motion controls, and the five mini-games in this killer app ensured that millions of people instantly understood the appeal, usually with massive grins on their faces the first time they returned a serve or bowled a strike. Without Wii Sports, there would be no Wii; without the Wii, the videogame landscape would be dramatically different. –Chris Kohler

7. Bejeweled (2001) ——————-

Among all the things that happened to gamers during the decade, having to fight with our moms, wives and sisters for computer time is one of the strangest. It's hard to nail down a specific game that bears the most responsibility, but for well over 100 million people, the gateway drug was PopCap's gem-matching puzzle game Bejeweled. (As famously parodied in an early Penny Arcade strip.) –Chris Kohler

6. Halo (2001) —————-

Nintendo's Goldeneye 007 was the game that took multiplayer first-person shooting on game consoles and made it mainstream. But it was Halo that truly rallied the troops. When the futuristic shooter debuted alongside the Xbox in 2001, its well-tuned controls made Halo the rallying point for a new generation of gamers. Of course, the tangle of CAT-5 cables at every Halo LAN party was also ground zero for the culture of frat-boy gamers that plague Xbox Live. You win some, you lose some. –Gus Mastrapa

5. Brain Age (2005) ———————

The '00s were shaping up to be the era of the big-budget blockbuster game. Development teams made up of hundreds of people would spend years and millions of dollars on productions that would rival feature films. Yet one of the most emblematic games of the decade was produced by a team of nine people in just a few months. Brain Age, an addictive series of puzzles, brainteasers and math problems, promised to be a sort of daily calisthenic regimen for your gray matter. The series has sold almost 18 million copies, roughly the same number as Grand Theft Auto: San Andreas. As a killer app that sold the Nintendo DS to a grown-up audience, it's the most extreme example of how Nintendo has bucked the dominant trends and made a killing doing it. Brain Age also ushered in the era of games that are (supposedly) good for you, like Wii Fit (over 22.5 million served). The game might be based on dubious neuroscience, but it suggests that all neurons are firing properly at Nintendo HQ. –Chris Baker

4. World of Warcraft (2004) —————————–

The MMORPG had its genesis in the '90s with EverQuest and Ultima Online. But Blizzard's World of Warcraft blew them all away, taking MMOs from niche pursuit to mainstream passion. Besides establishing that a critical mass of players will pay $15 per month to play a single videogame if it is sufficiently complex, WoW created a gold standard by which all other massively multiplayer games are measured. By grouping players into alliances and guilds, WoW created strong social circles among its devotees, who are so deeply involved in the culture that they attend the yearly BlizzCon convention. The game has influenced many other publishers to jump feet-first into the MMO genre. Most, so far, have failed miserably. –Tracey John

3. Guitar Hero (2005) ———————–

Not very long ago, Red Octane and Harmonix were tiny companies producing Dance Dance Revolution control mats and experimental music games that critics loved and nobody bought, respectively. Everyone's fortunes changed when the two firms teamed up to create a rock 'n' roll game with a controller in the shape of a guitar. Similar games had been moderately popular in Japan for years, but had never really taken off. Guitar Hero was the sleeper hit of the year, and just as it was exploding, the two companies parted ways. Guitar Hero and Rock Band are the Coke and Pepsi of music games, waging an all-out war for market share while continuing to raise the bar for music games in general. The games are breathing new life into the music biz, letting artists expose their songs to a new audience and bringing in new revenue from downloads. But more importantly, Guitar Hero took music games from a tiny niche to one of the biggest game genres around. –Chris Kohler and Tracey John

2. Grand Theft Auto III (2001) ——————————–

Few games this decade generated such controversy – or inspired so many other designers. Yes, any game released a month after Sept. 11, 2001, that allowed players to kill civilians and public servants was certain to be controversial. But beneath those attention-grabbing elements was a revolutionary open-world gameplay system. Grand Theft Auto III defined the "sandbox," a sprawling playground with sports cars instead of swingsets, rocket launchers instead of monkey bars. Players weren't forced to advance the Scarface-style criminal narrative; they could just amuse themselves in Liberty City. Forget the avalanche of clones: It's hard to find any third-person action adventure game nowadays that doesn't crib at least something from the GTA formula. –Daniel Feit

1. The Sims (2000) ——————–

It's the most popular game franchise that debuted this decade, with more than 100 million copies sold. Yet many people don't even consider The Sims to be a game at all. Will Wright's people simulator so completely disrupted our beliefs about what a videogame had to be that non-gamers with no expectations had the easiest time wrapping their heads around it. Sims has had a profound influence on videogames in a dozen different ways. The simplified human models with their carefully calibrated hierarchies of needs were revolutionary. The open-ended, accessible game design was the cornerstone of what came to be known as casual games. It was a sandbox game of unprecedented flexibility, allowing every player to create his own goals and play style. It was a platform for both modular add-on packages and user-created content. It was a highly visible property that was ported to every platform in existence, and is the basis for an upcoming feature film. The Sims, to a greater extent than anything else released this decade, broadened the definition of what a game could be. –Chris Baker