Alot of Halo haters ... being a huge Halo fan I cannot help but say it's awesome. Nor do I agree with it having not changed from Halo 2 much. The equipment you can use now is a huge addiction compared to 2. The control scheme for Halo 3 being completely different due to the controlers is nice too, nothing beats the feeling of being able to reload each gun seperately when dual wielding.
As for the person who mentioned the bad melee system, they've updated it now to make it ALOT better. Aka if people have taken similar damage they can both die, and even if one person wins, they still take damage. Makes it much better.
If you don't like custom games, don't play em, the game gets very competitive on the higher ranks, try playing it enough to get to that stage.