Quake 1 (Score 1, Insightful)

The game that spawned the online 3d FPS genre. The game that first popularized modding, CTF mode, teamfortress, and the other modes still in use in various quake descended games today. The grandfather of halo, counter-strike, and everything in the future. The game that defined a generation. Up untill today there is still Quake 1 servers online.