Highly agreed. I love Halo for the Forge, saved films and screenshots. I love TF2 for madcap fun. Half-Life has the best FPS story ever. But with all that said, FPS is getting to be like 2D fighters were in the 90's - every week, 5 more come out, each more uninspired than the last.
There's a paradigm shift coming, however, and it goes by the name of Mass Effect.