Well the story is there but it is very very badly told and derived. The first one had a very lackluster start to the story but it kinda came along with its twists and ended up being a simply but unique story. Halo 2, on the other hand, completely turned it around making it a complicated set of events. Added things with no background information and through things in that seemed random.
Halo 3 kinda went back to a more simplistic way of telling it but you still felt disconnected from the first one. There was no progression whatsoever. Really all 3 could have been their own game (aside from 2's cliffhanger). They needed better progression and much better flow. Typical, though of most shooters which seem to have spur of the moment story plots that have highs and lows at random ties.
I still think it was a good story but very poorly executed.
