I usually take in my games for store credit, or trade them in for other games after completing them. Unless it's a game I really enjoyed, or it has good multi player/replay value, I will keep it (FF, GoW, CoD, Halo,TES III & IV,)

I have also gotten cash for some of my games, but I always wind up regretting it because they give you less of a percentage of what it's worth if you take cash rather then store credit. And what do I go buy with that cash, MORE GAMES