Single player in Halo 3 was ok if you (like me) skipped all the cutscenes.
not playing Halo 1, and only playing Halo 2 online was the deciding factor in that, and most of the single player was good, apart from the bits Halo used to pride itself on, the driving.
now, for this I get 2 distinct options, drive, and have my retarded AI partner shoot at the weakest enemy who couldn't be any further from my vehicle if he were in fucking orbit, or shoot, and have my retarded AI partner drive in circles or come to a total standstill next to the mahoosive tank of death that I'm desperately trying to destroy with my piddly little chain gun.