Pioneered: Strong story experienced entirely from a first-person viewpoint, faceless main character, headcrab crowbar-smashing, even easier and more comprehensive modification by users than introduced by Doom.
Influenced: System Shock 2, Deus Ex, Call of Duty and every other story-intensive, mostly cutscene-free FPS.
Why it qualifies: Arguably the single most beloved PC game ever created, Half-Life took a genre known mainly for mindless violence and online competition and turned it into a strong vehicle for storytelling. Putting players into the shoes of Gordon Freeman – a character who’s never seen or heard – it threw players into the center of a sprawling, near-seamless research complex that was quickly overrun by extradimensional horrors and military black-ops squads. And as the world falls apart around you, the game tells the story entirely through interactive events that unfold around your first-person perspective; there’s no pausing for cutscenes here.
As beloved as its single-player campaign is, Half-Life’s real strength was in the ability it gave users to reshape the game to their liking, creating not only new levels and game types, but entirely new games. Counter-Strike and Team Fortress Classic were perfect examples, and proved so popular that Valve actually published them as official add-ons. The game was nothing short of revolutionary, ushering in a new age of story-centric shooters and user-created content that permanently changed the topography of the PC game industry.