I'll stick to this generation, but these stick out most to me whether my expectations were inflated or not...
Halo 3 - Worst Halo game I've played in the series and I've played all but ODST.
Fallout 3 - First time I've put hours into something that had zero enjoyment or fun with
Code of Princess - Personal expectations were set too high. Large reason why I wanted a 3DS.
Street Fighter IV - Given hope from friends and I hated it like all of the rest of the series
Borderlands - Was a chore to get through and wouldn't have done had it not been for co-op
Dragon Age - Similar feelings to Fallout 3, but it was just boring and not fun
Star Ocean IV - Worst JRPG I've played possibly ever
That's what I can think of off the top of my head for games that seriously disappointed me.







