Bioshock 1 & 2

I really can't choose, a lot of FPS games had awesome campaign modes this gen but I'll try to list my favorites:
(not in order)
- Half-Life 2: Episode 2(best ending EVER)
- Portal
- Bioshock(very creepy and awesome but what held it back from being the best was how deaths had no penalty whatsoever)
- Halo 3 (surprised me at how awesome it was especially the vehicle sections, best played with co-op)
- Rainbow Six Vegas 2
- The Darkness (really underrated, it has a really good story and the abilities were fun to use)
- Resistance 1 (pure arcadey fun, just like Halo 3)
- Crysis (the suit and stealth mechanics were fun to use but it kinda went downhill after they introduced the aliens)
- MW2

For me, it's between:

-Battlefield: Bad Company 1
-Bioshock 1 & 2
-Borderlands

Killzone 2 :).

Though I liked resistance 2 a lot also :).