Skyrim -- PC can't run it too well, I'm at the point where I can't fight half of the enemies without needing to dripfeed health and protect Lydia from dying
Fallout 3 Broken Steel DLC -- just lost interest in Fallout 3 as a whole
Oblivion -- haven't really started it, plus the archery and magic aren't that good
Call of Cthulhu -- last stealth section with no guns is absolutely annoying
Dues Ex -- PC almost can't run it at all
Fable 3 -- second half, the 'ruler' half, is way too unexciting
Fallout New Vegas -- got sick of it because I was sick of the Fallout playstyle as a whole by then, probably still am
Half Life Blue Shift -- it was just more of Half-Life gameplay, and I had my expectations raised by the pants-jizzing beauty of Opposing Force
Mass Effect -- didn't feel like I was accomplishing much, game simply felt too... 'huge' I guess, and the playstyle wasn't for me