I don't see why the majority of 360 fanboys (Muffinator included) think Halo is the game of games. I'm not saying it's a horrible game or anything, it's just that it received way too much hype for being a slightly above average shooter that managed to incorporate coop quite well.
The multiplayer aspect if definately fun, but it is not worth the game alone. If you're truely looking for multiplayer experiences, go with games like UT or COD4.
As for the single player, well there is quite a bit to be desired. I'm sure many people will back me up on that.
Now you may say that H3 has the forge, videos etc. etc. etc.
Congratulations, you're basically where the PC was at about 3ish (maybe more) years ago. Again, nothing special.
As for graphics, well, graphics don't define the game, but you would think that for the most hyped game for the 360 they would have wanted to crank up the specs a bit. This is nothing major though, and hardly a downpoint.
Halo is by no means a bad game. I'm just saying that it doesn't deserve the hype it gets. Games like Bioshock, The Orange Box deserve higher praise any day.
Also: this is just a thought about Halo. No comparisons to the PS3 etc.