As far as the worst I've played.....I find the FPS genre pretty bland in general. Bioshock is the only one I would consider exceptional. I hear good things about Half-Life as well, but I've never got around to playing it. : (
As some people have said, Haze was pretty bad from what I remember. As dandd just said, Area 51 was awful as well. I don't remember if it was an FPS, but also Clive Barker's Jericho....some great ideas that were poorly executed.
As far as popular games, I would say Crysis 2, Bulletstorm, and Battlefield 3.... I wouldn't consider these games awful, but I also thought they had some serious issues as far as single-player is concerned.







