IDG Answers is a community of experts who are passionate about technology. Ask a question or answer one below.
Ebay is easy if you have an existing account, and even if you have to set up an account, it doesn’t require much effort. If you don’t have a history of positive feedback, you might get a little less for your stuff because people won't feel as secure about your items/descriptions. Trade in is the easiest, but you get a lot less in return. If you have rare titles that are in demand, Amazon is another option. They also do the trade in, and make it even easier than game stores - just pop it in the mail and get an Amazon credit once it has been received and verified to be in good condition. You can also list items for sale on Amazon but I personally use ebay most of the time.