With the succes of Halo: Combat Evolved Halo 2 had a lot riding on its shoulders.
Halo 2 graphics could be a bit smoother cause it's kinda rough.
O and lets get back to the game now...in single player your marines/ODST (ODSTs are oribtal drop shyock troopers) allies will be able to drive vehicles (not just ghosts like they did in the last game) they can drive warthogs (with you in the passenger and gunner) and they can even drive tanks (which no longer have side seats for you to sit). O and Wraiths are pilotable (is that even a word?) this game and you can now board all vehicles!!!(except stationary turrets). And you can now wiedl the energy sword!!!(which is easily the strongest close range weapon and is just a 2 kill on legendary for elites and brutes) There are quite a bit of new weapons and vehicles but...i'll leave you to figure them out when you buy Halo 2. this game is overall one of the best FPS games out there and is must for some FPS fans who like a story along with tons of killing.
o and don't go around saying you got skills (cause most of the time u don't) and peple will flame you. And you can super bounce (due to the fact that halo 2 uses a different game engine,i think, and on Matchmaking is sometimes considered hacking which it obviously isn't only noobs will say that and ppl who say it's cheap well they better learn how to superbounce to cause bungie isn't gonna ban some1 for using a glitch and it's already stated on their website that no1 will be banned for the use of super bounces but is being monitored) before calling some1 a modder be sure to run various test or figure out what weapons he/she is using and how long it takes for you to die (member ppl can be very fast with a weapon but....modders well make it so they win just to see a number....yes thats right a number go up. for modders a bigger number represents how many balls you suck in a hour,or less, ) i only find modding to be ok when it is used in custom games and everyone agrees that it's ok to play with the mod or when the mod is just for single player entertainment and or multiplayer entertainment with ur friends on custom games. If you see a modder on XBL right down there gamertag then immediatly leave the game or you may be accused of supporting modding on Match Making. then send some feedback which bungie will look at and monitor the player's Matchmaking status and stuff (i dont really know).
just be careful there's also racism and constant flaming, it's probaly best if you don't talk much...or at least talk with the wrong people (being ppl shouting racist comments and ppl who constantly flame others, these ppl you can calll noobs even if they have a high legit number cause they're being f*ckin gay!!!!!(no offense to gay ppl sry if that did offend you tho) on a video game!!! and like 60% of the ppl that play halo 2 online are little kids and adults.....yes thats right you would expect some adults to be respectfull...well some are and some aren't...)
That's all i have to say...those are just some tips when playing Halo 2 online.