Prince of Persia, FF13 or RE5... Though choice...

I'll say FF13

Resistance 2

My vote for worst sequel goes to Resistance 2
Resident evil was bad too, but not as bad

and I really don't understand all of the MW2 hate.
I fully disagree with every negative point about that game.
sure, the story might be a bit macho or lame in parts, but most fps's are. The multiplayer is what it is. It just so happens to be the most popular game in a long time, it is more arcadey/ camping then Battlefield but that is just its style. And it is a lot of fun.
People... you don't always have to be an anti-conformist. Things are popular for a reason!

( and i just answere the question the same way the op did, i guess he meant most dissapointing)

Fable 2 - Yeh it was semi fun but no where near as groundbreaking for me as the first one....

MGS...nnah just joking.

Honestly RE5.

Tales of Symphonia: Dawn of the New World - Emil did something I didn't think possible. He surpassed Cloud as my least favorite protagonist in gaming history. Emil took being Emo to super human levels.

Resistance 2: The single player was terrible. Resistance 2 has some of the worst single player AI I've seen in recent years. It was like playing a mid to late 90s fps. All the enemies just ran straight for Hale whether he was in their line of sight or not.

Perfect Dark Zero: The original PD had a far better single player campaign and the new stylized art style was an Epic fail.

King of Fighter XII: The sprites weren't really HD, some of the characters were half finished, the roster was too small, the game modes were extremely basic, there was no Mai. SNK what the hell were you thinking.

I see many people voting for PoP but it isn't really a sequel to any previous title...

oh hell GTA IV worst game ever this gen hands down.

resistance 2

Tales of Symphonia Dawn of a new World