@Big Dumb Bunny: "I must be the only person alive right now who is totally unimpressed with this game." Yep, pretty much. You criticise Halo 3 for having a short campaign and graphics that aren't "up to par" but really, who cares when as you said yourself, the gameplay is excellent? The campaign of Halo 3 IS short but it is also very replayable in a way that Halo 2's was not, regardless of its lengthiness, thanks to its extensive metagame and cooperative options. Besides, looking at your Xbox.com profile you haven't even completed Halo 3's campaign. So how could you possibly know how long it is? If you're going to bash a game solely on the basis of its graphics and levels you haven't played yet, then you only embarrass yourself.
Lord_Alan's comments