i dont no!
You obviously have to pay for the game, but there are no fees for playing online.
In my opinion, you should hold on to the other games if you can, but more people will be playing on the newer games online.
Yes as long as its compatible with Modern Warfare 2
No
Mostly on the campaign no but if your on multi or online playing you can be on Search and Destroy.
Yes
Yes, there is online multiplayer on Call of Duty 4: Modern Warfare.
On PS3 it is, you'll have to pay for xbox live when you're playing on xbox probably
there is none
Just go online and play a game mode... you'll be playing with multiple players.
You cant!!!!!!!!!!!