As a buyer and a seller, wipe it. The chances that the games will appeal to a random buyer are fairly small, people have widely differing tastes. *IF* said games are pirated, you run the risk of some annoyed buyer reporting you. Or for having the buyer feel that you, the seller, are a slightly shady character to deal with, since they could assume possible pirating, even if that is not the case. That can be a real turn off to an honest buyer!
At the least, you may annoy the buyer when they have to delete your content. How does the buyer know whether your content is safe or possibly contains malware? If the games are not pirated, the buyer can find and load them on their own if they want them.
I just bought a used Kindle, and was quite annoyed to have to go delete a bunch of the previous users books.
Best bet for added value is accessories like cases, spare chargers, that sort of thing.
Sent from my Nook HD+