Fallout New Vegas. Though to be fair, I went into it without having every played any of the other games, and didn't really know much about it, but the few videos I saw of the game of all the different things you can do in casinos made me interested. But upon starting the game, I was greeted to an empty desert, and any attempts I made to get to the actual city part of the game were stopped by some sort of creature that would always kill me, and I realized I actually had to spend time out there and get to a higher level before I was able to get past them. I probably didn't give the game very much of a chance because of this, but that definitely turned me off from the game as it wasn't what I was expecting at all.
Ha-ha, most funny complain i ever seen. How old are you ? Ten years old ? If not, you are dumbest person in the world, you know :)
Only speaking for single player campaigns, Gears Of War 2 and Dead Space 2. Two games I had very high expectations for because the first entries were so good. Still two good games but I found their predecessors incredible. I have to mention LA Noire as a close third because I did really enjoy it but the replay value was too low at the time. But, now I can appreciate the game much more and would love to play it again.