Amazon may be better.
You can go on Amazon and check their trade-in prices on each game's page. I traded in 4 games a few months ago for about $75 when the same ones were gonna get me less than $40 at Gamestop. Amazon pays for the shipping, you just print out the label and send it off.
Plus, Amazon credit > Gamestop credit because you can get anything on their site as opposed to just video games.
This post was edited on 10/10 at 7:12 am