Great multiplayer, but a disappointment if you don't have Xbox Live. A short campaign, shallow weapons, and stupid A.I.
Halo 2 picks up after the last one. You are, again, Master Chief. Your ship is attacked(again), you escape with Cortana(again), head to Earth, an entire city is destroyed, you're an alien, go against other aliens, are M.C. again, find another Halo, kill some aliens, become an alien again, kill some flood, the bad guys get the index, M.C. again, kill some more, end as alien with a MAJORLY disappointing boss battle. The single player campaign is ABYSMAL!!!!!!!!!!! The only good thing about it is co-op. Makes the campaign slightly better, but cannot salvage it from a black hole of crappiness.
The multiplayer is pretty cool, but without Xbox Live, it's something you might play once every three months. I've only had the chance to play with 6 other people via system link. It's pretty fun, but gets boring after 2 or 3 rounds.
Halo 2 might be THE MOST OVERHYPED GAME EVER!!!!! I'm not kidding. I'm simply unimpressed by it. It has stunning graphics, dual-wielding, and some new vehicles, but it's all been done before. I'm giving it a 5 because without Xbox Live, you're pretty much screwed. Don't take Halo 1 out of that disk tray just yet. Halo 2, don't play this game.