halo 3 didn't live up to any hype. I found it quite disappointing. As for MW2, it lived up and went further than my high expectations for it. So yea I'd say there are some games that do
I know MW2 looks great but games like assassins creed and fable although they are still great games didnt live up to the hype (hopefully AC2 will). This means that people only or a least mostly buy the big games rather than the hidden gems. I love Eternal Sonata and it is very under rated.