hm, i have to say F.E.A.R. should be one to check out. it has really great action and the best slowmo effects i have seen, though it kinda lacks in creativity. There is only about 4 bad guys you fight, all look the same, level design is great. A bit short though. Doom 3 is good, not the best. REally great graphics engine but not very fast paced. Counter-Stike source is probably the FPS i play most, really good, but only fun for multiplayer becuase it's aimed towards online play. Half life 2 is one you should really get, though a bit outdated it still one of the best single player experiences i had. HALO is a pretty strong on single player campaign as well as multiplayer. hope i helped.