What I liked
I had a fantastic manager for the first 2/3 of my time working there, as well as some great co-workers. My second manager was also very experienced, but I could tell that GameStop was going through a lot of changes, some good and some bad.
I really enjoyed the conversations that I had with our regulars - it was so fun to talk to people that also really cared about video games and systems! There is also a lot of overlap with cartoon/anime/etc. fans, which was nice.
Sometimes you could win free games from the different developers if you kept up to date with your Level Up, which was a quiz program with information about new releases. You could also get leftover bonuses from new releases if they oversent or if people didn't pick up their bonus items (like pins, posters. etc.).
The work wasn't super demanding at my level since I just had to interact with guests, answer questions, work the register, and organize games. Sometimes my managers would try to get me to do other jobs that weren't in my description or that I literally couldn't do since I didn't have the right access to the computers, but it was mostly a non-issue.