As intresting as the aribters aspect of the story is in halo 2 (and its only intresting because you kinda get to see what the covenant is all about), the game wouldve been more of a success if it followed masterchief the entire time. A lot of intresting story/plot sequences couldve been inserted IF we didnt follow the arbiter in Halo 2. The Arbiters story wouldve probably made the game more of a success if it was an add on to the game, like maybe if it was included with Halo 2's first map pack or something. Because without the arbiter on the main game, they couldve put in a lot of kickass shit following the chief, meaning that all the arbiter levels would of course be levels replaced with masterchief's, also making the game feel a lot longer.

However this is just my look on the game, A lot of you might like the arbiters side of the game, i dont know.