Assassin's Creed - especially looking at the sequal (game looks good, but where's the continuity?)
Devil May Cry 4 - Nero needed to die
Fable: The Lost Chapters - I just didn't understand this one
The Path - Each character had awesome endings, didn't like the extra bit tacked on at the end
Super Mario Galaxy - seriously, that was just dumb
on the other end of the spectrum (ie. good endings):
No More Heroes - "too bad there wont be a sequal!" hilarious!
Bioshock - corney I know (good ending) but actually sweet, and 'badass' for the evil ending
inFamous - I have only seen the good ending, but i thought it was pretty cool, especially if you listened to all the dead drops
Prototype - it was predictable, very predictable, but the last boss was fun and Alex was still the crazy bastard who liked to grab people, run up buildings and throw them off into the distance
Prince of Persia: Sands of Time - I loved that ending, perfect way to finish the game!