Assassin's Creed 3 - The only Assassin's Creed game I couldn't finish. The game just made me lose my spark for the series in general.
Prototype - I usually love these type of games like the Incredible Hulk Ultimate Destruction. But this game couldn't hold my attention for long. Probably because being the Hulk is ten times more fun.
Half Life 2 - I honestly don't get what the big deal is about this game being praised as toilet paper's next coming. The gameplay was pretty meh to me (no thanks to that horrifically boring airboat level). I'm sure the story is good, but I just can't force myself to go through with it and like this game like everyone else. Never got past Ravenholm and not because it's difficult or scary or whatever (like what people seems to label it as something to compare to Halo's Library) it was just boring!
Fable - Guess it didn't help I started playing this series from the third game (which was apparently the worse game of the series). Good thing it was just a free game on Xbox LIVE. Still, this entire series in general could never grab my interest.
And then there is the list of games that I really did enjoy but couldn't finish for some reason. I just get to a point in the game (sometimes quite far into it), tell myself I'll play it again later, and then never play it. And I really want to play these games but I just can't! Mirror's Edge, Dishonored (I am at the very end of it), Far Cry 2, Far Cry 3, State of Decay, Just Cause 2, and a crap ton of games on the PC. Don't get me wrong, I have nothing against these games. I consider Dishonored an absolutely fantastic games and if not one of my favorite stealth games I've played. But I don't know, this habit is killing me.