Assassin's Creed 3.
I was looking forward to the new setting, main character, and improved controls, especially since Revelations was a major disappointment. Turns out, Connor ended up being the most boring main character in the series, side missions became even more trivial, your Brotherhood became less useful, the Templar conflict became more muddled, hunting became a chore, Revolutionary-era America not as fun to dick around in that Renaissance-era Italy was, main villain was mostly a bore....They somehow managed to make Desmond more fun to play as than Connor.
The game isn't bad, but it is only just slightly better than the let-down that Revelations was. After not playing it for weeks, I had to force myself to beat the game just to get it out of the way and move on to the next title (Far Cry 3). AC3 convinced me that Ubisoft should kill the annual release schedule for the franchise and give it time to really live up to the potential, similar to the transition from AC1 to AC2.