off the top of my head..
Bioshock (feel free to find one of my several rants on why I uninstalled it about 3/4ths in)
Oblivion (too.. much. Also: Ohcrap, not another gate, please!)
Dragon Age 2 (Basically "Yeah, it's fun listening to you guys, but I've really been here before too often")
Skyrim, probably (yes, timetravel here, but I'm certain it will share Oblivion's fate)
edit:
the Witchers (quit the 1st one after all that running around trying to find the right NPCs at the right time, back and forth, back and forth became sooo tedious. Never really started the 2nd. Think I'm a little behind the first tutorial bit)
Farcry 2 (but I don't remember the reason - might pick it up again)
Limbo (Nope, you die. Try again. Nah, idiot, try again. Meeeep! Try again, ...crap)