I'm not a gamer either, but i suspect most games are controlled by server connections with no p2p connectivity.
If I were building the kind of games you see depicted on Big Bang Theory, the gameplay would be through the server; but the chit-chat with the headphones would be p2p. There's no point routing all that chit-chat through the server. I guess you could play the game without the headphones; but it would be difficult to coordinate attacks with your partners.
When I thought about this a bit more, it occurred to me that the person being DoS'd should contact the game company. Now it gets interesting.
The game company has two aspects of its reputation to defend. 1. It doesn't want players being DoS'd. 2. It doesn't want to LART players based on spurious accusations.
That means it would have to make sure the suspect is guilty. They could have the user switch IP several times, and only display the new IP to the suspect. If displaying the new IP to the suspect resulted in the DoS being redirected, but displaying the new IP to other users didn't, then that seems like a smoking gun to me.
Now we get into the whole cost/benefit analysis for the game company to do something like that. It's probably easier just to log complaints against users, and pull the plug on people after N complaints. If say, 8 users from different walks of life have complained that X is DoS'ing them because he got pissed off, then there's a pretty good chance X is guilty. The best thing about this approach is that it works for all kinds of bad behavior, not just DoS'ing. You're going to have to handle complaints about users anyway, so there you have my answer for now:
Complain to the game company, but not until you've checked to make sure that something else isn't compromising your system..