You mentioned games you've bought or redeemed, but what about games you've received as a gift or found randomly? I used to recondition vehicles at a car dealership, and when we found stuff in vehicles we got from auctions or whatever, we could just keep it because there wasn't a quick and easy way to track down the previous owner. I have a bunch of handheld games from that. Mostly bad tie-in games (Incredibles for GBA, somehow both Cars and Cars 2 for DS), but also some good ones (like Mario & Luigi: Bowser's Inside Story).
I'm also curious about games you've bought in the past, but no longer have.
Regardless of the answers, this is something I would have to seriously think about. Like, that money would be life changing in a good way, but that restriction would also require me to change a lot of aspects of my life I don't want to change. Mostly in regards to my current social life, since that's largely related to hanging out in Twitch chats.