Call of Duty World at War, Modern Warfare 2, Black Ops, and soon-to-be Modern Warfare 3. Seriously, CoD4 was the last good CoD game.
Gears of War. Had it when I had an Xbox a few years ago, tried it once, beat first two missions, utterly and completely lost interest. Thought it was just me, tried it again 3 months later, hated it more. Friend brought over Gears 3 the other day, and I still absolutely hated it.
Halo 3. I beat Halo 1 and 2 and loved them, but Halo 3 was such a snore-fest, I only got half way through. ODST was also lame as hell, and Wars is a total waste of time. I think I'd really like Reach, but I don't have an Xbox anymore, so. . .
Oblivion. Snore.
Assassin's Creed Brotherhood. Goodness gracious, more of Assassin's Creed II, which I was totally done playing when I got around 91% trophy completion (I was going for plat, but just couldn't bring myself to keep playing)