I have had some disappointment in the last years...
Uncharted 3: I loved the first two games so much that I platinumed them, and it was hard, believe me. So, for the third game, I wanted to unlock a lot of things, like unlimited munition or the invincibility like in the first two games but I didn't find any of that after I finished it. There was no incentive for me to replay it. That's why I didn't buy the other games, I love secrets and I love to unlock things.
Horizon Zero Dawn: it was boring and bland, and the battles were a little too hard, too intense and too bow-focused for me. I wanted something more relaxing. Sure, it's a beautiful game, but after playing it for one or two hours, I found out that the map was empty, there were only herbs, machines and quests. No secrets, no funny easter eggs, no surprises, nothing interesting. In fact, it reminded me of the beginning of Morrowind and the guy who fell from the sky after using the spell of Icarus I think; there was nothing like that.
Street Fighter IV: I liked the game, but I was disappointed not because of the game itself but because of external problems. First of all, it found it hard to play, especially because of the focus mechanic. I might have tried for maybe 10 hours or more in training and in real play, but I never was able to do shoryuken > focus > ultra with Ryu when I wanted, and I always play with Ryu in all Street Fighter games. And also, because of where I live, the online was simply impossible for me. But that, I discovered it after buying the game. And because of all of that, SF4 is the game that made me stop playing fighting games.
The Witcher 3: the battles. I'm sure I don't have to elaborate.
Watch Dogs: what do you want me to say?