I've got both, and like the 360 better for games, since XBox Live totally kicks the PSN's ass. The PS3 is my DVD Player of choice, though. I bought GH3 for the PS3, thinking that I could play GH1 and GH rocks the 80s on it, but as someone said, the guitar doesn't work. If you buy GH2 on the 360, you can download some of the GH1 songs, though. I've not been on Xbox Live a lot lately, but when I start my new project in a few weeks, I'll be back out on the road, and I'll be grabbing CoD4.
Does anyone have a Wii, with Super Smash Brothers yet?