For the xbox console I would recommend xbox.com site. It is run by Microsoft. EA.com is a good site for different EA games played on the PS2 and the xbox. EA.com is also a good site for the EA sports games. They have good forums there also.
For the PC each PC game normally has their own site that has forums.
IGN.com is a gaming site for the consoles and PCs and they maintain forums for talking about the different console or PC games.
Here is another good site which may be good to visit for the users of this site for talking about gaming.
For xbox360 gaming, I'd recommend www.onthespotgames.com. It's a website dedicated to xbox360 gaming, with an emphasis on home theatre systems and High Def gaming. Plus, the guys are really cool.
Anyway, just thought I'd let you know. Sometimes it's tough to find adults who like to game!