1 and 2 are totally different games...
I would say I prefer Halo 2 for multiplayer because it doesn't have the pistol bullshit. I was pretty good at it, but I always thought it was sorta lame that the pistol was so accurate. The guns are much better in 2, except for that fucking lame sword. It's also way too easy to stick people with plasma grenades in 2.
The vehicles are way better in 2, with the damage and everything. Way more fun, plus there are more of them.
I liked the single-player in halo 1 better though... the maps were way bigger and more open-ended. I think what happened is that they spent too much time on the art in halo 2 (notice how everything looks better) but they didn't put enough time into actually building the levels, so they're really linear and while all the architecture and everything looks great, there just isn't the depth halo 1 had.
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i never wash my hand. hell, i eat pizza while i'm taking a shit.
-seanPISTOL