I see what you mean, I think Halo 3 was too awesome, and the gap between 2 and 3 was so great, that we feel let down by this new iteration because the difference isnt the same.

Jetpack isnt as cool as trailers made it, or at least thats why I feel. Its not really that useful.

Then again, I'd pick to play Halo Reach over Halo 3 right now.