Halo: Combat Evolved (2001)
More than just introducing Master Chief inarguably gaming's most iconic space marine Halo: Combat Evolved made Microsoft's fledgling Xbox a real contender in the console wars. Its spot-on controls and sprawling sci-fi story also proved you needn't be a PC snob, exterminating extraterrestrials from behind a mouse and keyboard, to enjoy a genre-defining first-person shooter experience.