My Gamespot gives trade in prices over the phone...
also they give cash instead of credit if you want it, but it's less % than credit.
here are estimates for the games you listed:
-Project Gotham Racing $5-9
-Morrowind $8-15
-Amped ?
-Sega Gt and JSRF pack $6 each
-NBA 2k3 $4
-Turok $4
Tony Hawk 4 $15-20
Due yourself a favor and get a prepaid phone card for this and future calls to them.
Gamespot is alot easier than bothering with Ebay, you don't have to deal with checking the site everyday, waiting for your money, shipping the games out, etc, etc...
ok so you will make like 5-10 bucks less sometimes on a game, but it's much easier and satisfying to goto Gamespot, get your money in 3 minutes, and have a new game in under 6 minutes...
it's good to sell old games to Gamespot if they're rare, I got 50 bucks for Chrono Trigger from them