Let's see here... Do remakes/remasters count? Operating under the assumption that they do:
Bioshock (Xbox 360, Steam)
Bioshock 2 (Xbox 360, Steam)
Blue Dragon (Xbox 360 x2)
Borderlands (Xbox 360, Steam)
Duke Nukem Forver (Xbox 360, Steam)
Left 4 Dead 2 (Xbox 360, Steam)
The Legend of...