In 2004, Grand Theft Auto: San Andreas was a major hit. It sold millions of copies and was Metacritic's "Game of the Year," where it still has a 95 reviewer rating. Now, for $6.99, you can play it on iOS devices, with Android and Windows Phone versions expected shortly.

San Andreas isn't the first Grand Theft Auto game to make the transition to smartphones -- Grand Theft Auto: Vice City  and Grand Theft Auto III are also available as apps. And the mere fact that smartphones can handle what were some of the most technically and graphically complex games for consoles a decade ago hints at why smartphones are the best place for mobile gaming in the foreseeable future.

With over half of American adults owning a smartphone, there is a huge, built-in audience. And it's an audience that is already using their devices to play games, albeit mostly more casual ones, in large numbers: Angry Birds which had been downloaded close to 2 billion times as of September of this year. That casual edge could be a barrier: Smartphone users are used to paying pittances for games, not the $40 and up launch price point of most Playstation Vita or Nintendo 3DS games. But porting older games, as Rockstar is doing with the Grand Theft Auto Series and Square Enix is doing with the Final Fantasy series, could help gaming companies generate some easy revenue while they figure out the best model for marketing more ambitious, recently developed games.

Of course, gaming specific handheld platforms aren't likely to disappear immediately -- and there's probably a continued market for them for younger gamers whose parents might not feel comfortable handing them a fully functional phone. But in the long term, it's hard to see a mass consumer culture will want to drag around a gaming handheld and a smartphone, when the latter is more than capable of doing the jobs of both.