Would deserve a 10 if the single player weren't so short.
Gameplay - Has well refined halo: combat resolves weapons and only disappoints fans who so desperately wanted the pistol to return untouched. The multiplayer matchmaking systems and maps have set a new standard for games which people often forget and underappreciate.
If you're a bargain hunter looking for a singleplayer game to play i wouldn't expect too much from halo 2 and would recommend you buying halo 3 first. Worth playing in my opinion but halo 3 is essentially the same game updated so don't expect a huge multiplayer audience now that even halo 3's out-dated.
Since Halo 2's a heavily multiplayer oriented game it's quite a shame but you haven't missed out since like i said halo 3 is a very similar experience and almost feels like the same game at times.