With digital distribution I'd be very surprised if there were any real 'rare' games on 360 at all. You should see the prices people charge for a new copy of Parasite Eve. It's not even that good a game.
Ive got quite a few lauch titles and there worth virtually nothing although COD2 can still sell for around £20. Something thats 6 years old isnt going to be worth anything. For something to be valuable it has to be 2 things. 1- Rare and 2 - In demand ,
this game is neither and neither is any title on an xbox360