These 2 tie for me:
Halo 3 and GTA IV - both solid, but neither remotely coming close to the hype IMHO and both clearly not the 10 games they were made out to be (although the MP on Halo 3 was close to it the SP wasn't and I judge the game on both).
LBP I don't think you can judge yet just by its nature. Until we see whether the community takes off or not you're not judging the whole game. So far it actually seems to match the hype anyway - its fun, cute and allows a great deal of creative possibilities. I can understand people not liking it (that's the same for every game) but if I compare the promise to what (so far) as been delivered then it seems to have easily come closer than many other AAA hyped games this generation.
Try to be reasonable... its easier than you think...
