Wow, you really play a lot of games. If you didn't get SSX3 for the GC though, pick that up. It will keep you busy for a long time if you're going for the platinum medal on every event. I've owned it for 4 years and every year I pick it up and play it, and it is still just an awesome game.
Also, if you got a PC and 360 you should probably be able to find some other things to keep you busy for a while anyway. I wouldn't sell it. I thought of doing it with my Wii when I found out they were selling for $500 (I bought it at launch), but the shortages have gone on for a very long time, and apparently there isn't going to be a big drop in demand any time soon.







