What do you do when you complete a game? I usually hold on to the really good games or games that have a high replay value. For the rest I either sell\trade to a friend or hold my nose and list them on Ebay or trade them in at GameStop. Recently I came across another option that I think gives you the most bang for the buck.
Goozex is an online trading service that matches you up with others looking for the game you have. When a trade is completed you get a point value deposited into your account. For newer games you will usually get full credit which is usually 1000 points which is $50.00 to use to trade for games that you have in your queue. So far I have completed several trades and the process is very smooth. You also have the option of purchasing points but I don’t recommend this as you can get better deals elsewhere, but if you are trading an actual game you get a better value for it than you would anywhere else.
The fee for the service is only one dollar per transaction and if you are trading your game you pay the shipping to the customer but that is it which isn’t bad at all. In a day where GameStop give you nothing and Ebay’s fees keep climbing higher and higher this service is definitely worth looking into. Overall I have been very satisfied with the process. Check out the link the below for more info on the service.
Been There, Played That 
Sounds good, wish I would put effort in this. I try to get the newer games and let my brother and whoever else replay. I then Gamestop it for $10-$20. Maybe someone can start a service where they sell your games for you for a commission, for us real lazy people.
I have to agree about Ebay/Paypal. It used to be that you could get good deals on Ebay. But between the scammer’s and the fees, it’s just not worth it anymore.
I’ll have to check this service out. I way too often just hold on to my games until they reach $0 value.