Depends where you buy it from. EB Games here offer some kind of warranty I think, and they test the games earlier. If a game is missing a case or has obviously been mistreated, I wouldn't buy it. But I don't buy used games too often anyway.
THERE WILL BE NO BEK LEFT BEHIND! ~Pyro I <3 my bear
Everyone raves about Gamefly, but don't they put put one of those ID rings around the middle of the disc like Netflix does?
No, they don't.
It's been years since I used the service, so I couldn't remember.
In the past couple weeks I've gone to buy used games at different stores, and they've had these rings on them. Luckily they had more than one copy of the game, so I was able to actually make my purchase and get a disc that wasn't defaced. So this is fresh on my mind right now.
You should check the disc to see if it's in bad shape. If it is, then don't buy it and ask them if they have another one.
The real trouble is buying used xbox 360 games because those aren't blu ray. A slightly messed up blu ray disc would still work. I can't say the same for xbox 360 games. My used copy of a cod game has a few slight scratches and the 360 gets louder than normal when loading the disc (it's installed onto the HDD so the noise stops after a bit).
In addition it makes a weird hissing noise that continues as long as the disc stays in. Once I noticed this, I stopped playing that game. All my 360 games are new or digital downloaded.