For me, Destiny and MCC.
Destiny, despite having played many hours was a disappointment. I wasn't looking forward to the game for how many hours it will provide, I wanted something that felt compelling to play on my own at the very least, especially when they announced there will be no local multiplayer, and also expected Bungie to release a game that would compare in quality to their Halo games.
MCC, was looking forward to this being the definitive version, matchmaking issues galore, framerate issues in campaign, single player, and even worse in splitscreen (which I was really looking forward to). Not the definitive version I was hoping for, maybe with enough patches it can be, it just isn't there yet.
AC U I wasn't really looking all that forward to (so, hard for something like that to be disappointing) and the game performs okay on my PC. Driveclub I didn't plan on playing online at all, so the main thing I'm disappointed with is the club cars aspect. The game delivered on he gameplay, graphics, content front for me.