You gots to play this game with friends that know this franchise. Preferably local multiplayer it's a blast because KI plays different than other genres and it's super tactical.

God of War: Ascension, Castlevania: Lords of Shadow 2, Fable 3 and Gears of War: Judgment are the most disappointing because I love GoW, Fable, Gears and C:LoS but the latest games in those series were only mediocre (Fable 3, C:LoS2, GeoW:J) or just good (GoW:A).

Uncharted 3 & Gears of war 3 were disappointing since UC2 & Gears 2 were great but they are both still good games. Metal Gear Solid 4 was awful, really disappointing game but because I'd never played any of the previous games I didn't really care much. Halo 3 & 4 were disappointing. Bioshock Infinite was great but a little disappointing.

Bioshock infinite
Metroid other m
Mass Effect 2

I could mention a lot of names here, but none will compare to what I expected of FF XIII, and what I got. So, that.

Seriously?

Metroid: Other M, Last of Us, Papers, Please, LoZ: Skyward Sword and Twilight Princess, Splinter Cell: Blacklist, Mass Effect 3, basically any Resident Evil after 4 not named Revelations, Dead Space 3, Donkey Kong Country 3, Devil May Cry 2/Devil May Cry 4/DmC, Metal Gear Solid 4...

...maybe I get disappointed too easily.

Crackdown 2. Original was so good. Sequel was not terrible, mostly because it retained so many of the originals elements, but it was very meh in comparison.

Infamous 2. Hey guys lets take everything that made the first game great like good story, awesome characters, interesting city, and replace it with a shit story, boring characters, and a shitty city. Top it off with the most failed supposed to be epic but was boring as fuck boss fight ever, meh.

Twisted Metal 2012. The core gameplay was amazing, its too bad ESP and Sony rushed the game out knowing online play was broken. And since online was the main mode, yeah. Brilliant.

I try not to expect anything from a game before I played that, but having said that...

Uncharted 1& 2 disappointed me. People had hyped up the entire series as one of THE best for the 7th gen, so when I finally got to play them both... they fell short of my expectations. While not bad games at all, they felt very repetitive and the controls weren't all that great either, and the story wasn't as good as people made them out to be.

Mass effect 2 (PS3) - the frame-rate was shit. All that talk about optimising for PS3 was lies. - great story though.

titanfall (PC) - atleast I didnt waste money on this since I played the beta first. Massively over-rated and focused on allowing noobs to have more fun. Thats the only regard in which it 'reinvented the genre'.

Halo CE (PC) - boring as fuck single-player and the online was hacked to pieces.

I played more disappointing games, but I didnt really expect anything from them to behin with, like alone in the dark or legends of wrestlemania.

Super Smash Brawl, a good game but was a huge step down from Melee and 64.