Next PC game to play? Gears of War, GTA IV, Fallout 3, Dead Space

I'm an FPS fan. Just finished Far Cry 2 which I thought was both good and bad, and of course it had nothing to do with Far Cry.

I believe the games I'm considering (above) are all 3rd person shooters/RPGs or some combo of the 2, which I'm not sure I will like, but I don't know of a good FPS out now for the PC. Of the games above, which should I play?

Any help is appreciated.