I love Quake 1, definitely in my top 3 FPS games of all time, possibly in the #1 position. Sure, Doom might have been first (Wolfenstein?), but Quake brought such a level of innovation to the scene that it was the first true FPS similar to what we play today. Three dimensional support (jumping, mouselook, etc), awesome multiplayer (better than the new Modern Warfare games), Team Fortress, Quake Done Quick, etc. It was the first game that I can recall that had a HUGE community developing maps and mods. To me, Half Life is the true successor to Quake 1 and no game has had more community development and support than those 2 games.