Hmm, I actually worry quite a bit about my gaming backlog, it's been kind of long lately. Some of the games on there are getting pretty old. I won't even think about the fact that when I was younger I only beat about 1 or 2 of my 40 or so Ps1 games. Just for 360 for the time being though, we have:
Alone in the Dark (I doubt I'll ever beat that.)
darkSector (Maybe one day on some down-time.)
The Darkness (I really should. I didn't get stuck, I just never completed it.)
Dead Space (One day.)
F.E.A.R. 1 & 2 (I didn't really like these games but got to the very end on both of them, and got stuck. Usually I leave the game and come-back a few weeks months and replay the game completely. With these I just had no will to.)
Halo Wars (This game pisses me off, and I may not ever beat it.)
Kameo: Elements of Power (Yeah, old. I don't know if I'll ever get around to it.)
Lost Odyssey (Love it. Need a strategy guide. Haha.)
Mercenaries 2 (Got stuck and just never revisited it.)
Lost Planet (Stuck.)
Perfect Dark: Zero (Could never get into it. Maybe one day.)
Ninja Gaiden II (Frustrated all to crap. Doubt I'll ever beat it but I'm sure it will get played more.)
R.U.S.E. (Lost a later mission once and took a break for the day. Turned into a break for forever.)
Sacred 2: Fallen Angel (It's so long, and so silly! I liked it a lot, but I just get so sick of it after a while.)