For some perspective.
In my hometown (Western Illinois area on border of Iowa), has a handful of local places for pre-owned games.
Gamestop - We have half a dozen in the area. As described, they're half merchandise now, and their selection has actually dwindled quite a bit in recent memory. They must be pushing hard to have low stock-on hand and only retain games that are going to sell for a minimum of $10+, at least that's the impression i've gotten in my area.
Disc Replay - If you tried to trade-in your Grandma, this place would probably accept it. This place is known for the sheer volume of offerings they have and is a great resource for games if you have time to look, but it's disorganized because they put every box on the shelf, sell so much stuff that it feels more like an overstocked pawn shop than a game store, and isn't necessarily a pleasant experience.
Local game shop - We have a game store that's been here for over 25 years, that has always been a little more expensive, but usually had a robust offerings of systems and games across time, neatly organized, and friendly staff. Since I moved back 2 years ago, They've taken a baaad turn to straight-out price gouging, having hardly any games prior to Playstation 1, and the most egregious thing I see is they've resorted to selling SNES carts with ROMS of fan-made games on them.
So...given my options, I don't think Gamestop is so bad, if they have what you're looking for.