Resident Evil 5. The reason I bought a 360 was just to play that game. Although it was an ok game it really didn't justify me buying a console solely for it. Luckily for me I've managed to get some great games for it since.
Also Skyward Sword. Really didn't get on with it. Played it for a coupe of hours then gave up on it. Such a shame considering I was so hyped for it.