Half life 2 is my all-time favorite FPS, Bioshock being in second place.
Also, stop counting Portal as an FPS. The goal of it is to solve puzzles, not shoot things to end their lives or destroy them. I might all well call Minecraft an FPS because t is in first person and you shoot arrows. The only reason you people try to deny Portal not being an FPS is because you're fanboys who need to mention that game at every chance.