I just wanted to say that CoD3 and GTA IV are playable online via XBOX 360.
In CoD3, if you hit someone on your screen they die. There's no visual sign of lag when your are walking or running.
GTA IV is playable, but only with auto-aim. Racing is also possible, but be prepared to see the cars 'slide' a lot.
You can't get the best experience with these games, but it's fun to 'participate' in them.