I enjoyed Sticker Star, but then, I never really thought much of the Paper Mario series in general (all the things people whined about w/ Sticker Star seemed to me to be flaws that had always been present).
But, anyway: for me, Luigi's Mansion. I was not expecting the gameplay to be so rigidly partitioned into short, small segments. Huge disappointment.
"...Blame this on the misfortune of your birth." -Char Aznable
Well, I thought Luigi's Mansion was great....for the first few mansions. Then it became a chore to play (IMO).
I was really looking forward to Donkey Kong Country Returns, but the framerate bothered me, the level design was brilliant in places but frequently annoying in others, the enemy design was lame, the variety in gameplay wasn't there, and I just didn't have much fun with it.
"gahh i cant post and hurt somebody but im not trying to." - donkeycoot233 unintentionally hurting feelings
Luigi's Mansion: Dark Moon. I wasn't expecting anything out of this "game", but after playing it, I was disappointed and it wasn't as good as most of the other 3DS Marios (let alone as good as the first game on Game Cube), in my book.
But as for one game I expected a lot out of (and to be disappointed), it would no doubt have to be Tetris Axis. I expect the multiplayer modes from Tetris Worlds to be in this, but my goodness was it a mini game fest of Tetris. Only the Bomb Party mode was fun, in my opinion. The rest of them tried to. I did manage to download this on eShop for $10, which is how much it should've costed in the first place.
Awaiting for NEW Paper Mario, Final Fantasy (Classic style), Kirby, Fire Emblem, Bomberman, and Mario Sports Mix successor on Wii U...
Fire Emblem: Awakening. Maybe I just suck at strategy RPGs, but the enemies just seemed too overpowered and some of the characters too weak (enemies can one-shot you in only the third level? what the heck?!). And it's far too easy to screw up a battle and have to restart; pretty much every other RPG I've played gives you more leniency in that regard. I doubt I'll be finishing that game.
Also Mario Kart 7. It was absolutely not worth the $30 I paid for it used. While it was a good game in its own right (some of the tracks were pretty cool), the fact that it's on a handheld console means you can't play multiplayer unless you do so online, and Mario Kart is just so much more fun to play with someone rather than alone. Had it been released on the GameCube or Wii or something, it could have been my favorite, but as it was, it just ended up kind of teaching me not to buy handheld Mario Kart games unless they're really cheap. Though at least it looks like Piranha Plant Slide and Music Park, my two favorite tracks from the game, are returning for Mario Kart 8 (though I don't plan on getting MK8 until the price drops anyway...).