I haven't played all that many FPS games, but I did finish Doom 3, which was really dark! Played quite a bit of Call of Duty on PS2, but joysticks own me in FPS. Been playing Ghost Recon recently, it's pretty fun as it's a bit more tactical. Also House of the Dead 4 at arcades is pretty fun, although I'm not sure if that counts as FPS. I think I liked Serious Sam 2, but that was quite a while ago.