UC1 is good too, though the screen tearing and lag (from what I remember) make it suck a little unless playing single player, which isn't really the point of the game.
UC2 has 3rd person, melee combat, Raiden and a bit of an Ancient Egyptian theme. It's also around 2150MB.
Anyway, ironically, I seem to be having a bit of trouble with my Xlink, but am working to sort it out, so I hope you guys play each other even if I can't connect. MSN me if you do want to play, as I may have sorted my Xlink issues, but can't test it out, as I don't have Halo 2, and that is all anyone seems to play on there.