Can't really say I played any major disappointments this year. The worst offenders were either good games that should have been great, or average/bad games I didn't expect much from to begin with.
Beyond: Two Souls would top my list. It was merely a good game and I expected it to be a toss up with Last of Us for my GOTY. Hell, I'd have been happy if it just managed to be a better game than Heavy Rain, but instead it took a step backwards in several areas.
Next would be Bioshock Infinite. I'm not a huge fan of the series, but I expected it to fix everything I didn't like about the other Bioshock games and it really didn't. The actors did a fantastic job, and I didn't hate the story this time, but the gameplay was just as tired and uninteresting as the rest of the series.
Saints Row IV too, I guess. I regret paying full price for it and screwing up my game by doing things in the wrong order and missing a bunch of stuff, because I was rushing to play through it before FFXIV release. By the time I got around to playing it right, I could have gotten it for $15 instead. The game itself wasn't bad but it failed to fix most of the issues I had with SRTT, and added a few more of its own (I really could have done without all the superpower stuff). Volition is still being lazy as hell by making story missions use side mission content far too much, and they are getting further and further from what made SR2 the game I consider to be the absolute best of its genre by a huge margin.
Thankfully, I was smart enough to stay far away from Aliens, and my refusal to use Origin saved me from the SimCity debacle. I own Dead Space 3 technically, but Origin has saved me from ruining my good memories of the series there too.
I'm saying people should expect a $20 title to be short.
ex. Blood Dragon @ $15....much shorter than FC3
$20 game, short campaign... fine. What isn't fine is that the editor is very limited in what it allows you to create, and that's why the user content is all pretty mediocre. And why the main campaign isn't just short but also lacking in depth and rather easy as well. At this point I've just about given up on it, and instead I'm hoping that Klei's Incognita will fill the void for a turn-based tactical combat game, even if the setting isn't nearly as interesting as Shadowrun.
Sounds like you played it for about 4 hours, it's definitely slow and hand-holdey in the beginning. Not say it was one of the greatest JRPGs of all time but it was pretty good and the Ghibli style visuals and story are a lot of where the hype comes from.
The game got even worse once the hand-holdey part ended and you got to experience a strong contender for the most retarded companion AI of all time.
I wouldn't put it on this list though, because my expectations weren't high to begin with.
Edit: Oh yeah, I forgot all about Cube World. I definitely regret giving those people any money too, and I will probably never support a game at such an early stage of development again.