Halo (2001)
This game, and the advances it represented in multiplayer gaming, helped make the Xbox a real force in the console wars. Multiplayer first-person shooters like “Counter-Strike” had been around on PC for years, but the genre hadn't gained much traction in the console market. Halo changed all that, bolstered by a strong single-player campaign. It's hard to step into the boots of someone called Master Chief and not feel awesome.
