As long as you have the spare time and nitpick, you CAN find good and complete condition games at GS. But be prepared to get the 'hurry up' look from the employees.....repeatedly.
I actually nitpicked on a copy of Sonic's Ultimate Genesis Collection for 20 minutes during a B2G1 a couple years ago and in the end I didn't buy any of the 3-6 they showed me. Every last one had some sort of scratches on them(for a PS3 game).
But I've bought plenty from their sales otherwise. Sometimes(it's rare) they have a good sale that you just can't pass up. But that's few and far between.