Looked around the forums a bit before posting this, but i think there should be a thread where people post games they love, and why they think they are under appreciated.
My contribution: SSX On tour (not the new one)
http://www.amazon.com/SSX-On-Tour-Playstation-2/dp/B000AOEUOI
Its like 5 dollars at any gamestop used for Gamecube / PS2 and it is by far money well spent.
I picked this game up this summer and holy shit, its one of the most enjoyable games i own. Although the game is primarily a snowboarding game, there is the option to ski. It really is fun as hell to ski SSX style, and honestly, for 5 bucks, you can't go wrong. If your looking for something to do, and you don't have the 60 dollars to drop on the new SSX game, def. buy this game.