Okay, did nobody read my post? First of all, online games don't transfer graphics. All graphics run from your system. The only things transferred during an online game are things like position data of the players, action cues, environment status, et cetera. It's just data telling your computer what graphics to show. Therefore, there really isn't that much data being tranferred. If the entire graphics of everyone and the environment were transferred, you would need a T1 connection to play smoothly, if not faster!
Here's an example:
You're in a room with two other people. One of them throws a grenade. Now the image of a grenade is not transferred. A tiny bit of data is transferred that triggers a grenade to appear on your screen. Your computer gets that data and says, "HEY! THAT MOFO THREW A GRENADE!!" Then it takes the grenade image ON YOUR COMPUTER and displays it at the appropriate time and place. It also displays the explosion animation that is also already on your computer. Now say the other guy jumps to avoid getting blown up by that grenade. His image is not what is transferred - it's the trigger data that tells your computer that he's jumping. Again, your computer receives this data and interprets it as him jumping. It then displays the appropriate animation that is already on your computer. Finally, let's say the guy who threw the grenade runs out of the room triggering the door to open. Again, the trigger command of the door opening is transferred, not the actual animation. So, the graphical data is not what is being transferred, it's much, much smaller trigger data.
I used to play Half-Life on dialup with no problems most of the time. Sure, sometimes I would lag a bit, but it happened rarely. Once again, I don't know how much data current games transfer during a multiplayer game, but I'm guessing it's the same, if not less.