2. Grand Theft Auto: San Andreas
Still known for being massive (though not as big as Just Cause 2), San Andreas blew GTA III and Vice City out of the water, literally quadrupling those games’ islands with several of its own cities and a countryside. Each of the game’s cities, modeled after Los Angeles, San Francisco, and Las Vegas in turn, had distinct flavors and personalities. The surrounding wilderness–far from being just open space–was also packed with different landmarks and activities. This was all supplemented by the myriad of new ideas in the game: flying planes, swimming, dynamic RPG character-building elements, burglaries, car customization, territory wars, and cooperative modes, to name a few. It’s practically impossible to run out of things to do in this game. Not everything in San Andreas worked, but it was the mark of a developer really putting in a tremendous effort to redefine the genre it helped pioneer. Some missteps with the game merely helped lay the groundwork for other open world games to come.