i don't know the answer to your question but i'll give you a little heads up. you seem like you might be new to this forum. you might want to get rid of the all caps in your title. some poeple get a little upset about that. FYI it's against the rules. no biggie, just remember that in the future.

no you cant play this game cross system .... the only game that i no of able to play across system was final fantasy XI and that was ps2 to computer .... though it would be sweet if you could

DURRRRRR!

with NFS Underground you could play crossplatform (PC, PS2. XBOX), thats the only other game that I know you could play crossplatform.. next year all EA /EA Sports games will be like that though

Are you trying to be funny or do you believe that?

As far as I know you can only play people with your console. Cause one of my friends has X-Box and I can't play him when he plays NFSU or T.H.U.G. online.

You are not a good liar.

Well I don't know when that will be possible, actually. Simple reason is that PS2 and X-Box use different servers. To my knowledge, most (if not all) X-Box users play online through the X-Box live servers. Just about every X-Box online game uses these servers provided by Microsoft, I think. I don't play X-Box online so I don't know for sure.
PS2 games are generally responsible for scrounging for their own servers, which seems to commonly be Gamespy or some other popular server. So simply put, cross-consoles probably won't happen simply cause each console uses different servers.
FFXI was an exception because both PS2 and PC players have to use their account on Square-Enix's PlayOnline servers.
I may be wrong, but I'm positive that if systems are on different online servers, they can't play with each other.