Very few single-player FPS games have any inherent replay value...ever. Play game, crank up difficulty, play exact same game except have to use more ammo to blow !@#$% up.
BioShock for me was one of those games that promises so much, and delivers so much, and then drops the ball at the end (I'm looking at you two in particular with that sentence, Fahrenheit and KoToR 2 -_-).
Atm I've started playing:
Though only in pitch darkness at night with the lights out and on the highest difficulty. I pee fear.