What's wrong with that?
What's wrong with that exactly? It's not like Game will have stolen the second hand copy back is it? As others have said, if you buy a car and sell it on, the dealership doesn't get a cut. However if you give it back to the dealer - new but registered - they can't sell it as new anymore, they have to absorb a hit on their profits for the sale. If you sell it back to the dealer - used but practically new - they'll make a bit more as they charge you for the use you've had, and then sell it for a little less than a brand new one. This is exactly what Game do, and they're within their rights to do it.
As for the publishers deserving an extra something back, their part of the bargain is to provide an online space for each copy of the game, for as long as there is decent support for it. If the original owner sells their copy, they can't play anymore, and so the online space for that game transfers to the new owner. It's still one space, per game, and still the same number of games in circulation.
Frankly I'll stop buying stuff for either of my PS3s, plenty of content is impossible to copy between systems, even if you 'officially' redownload it from the PSN store. While xbox might be doing the same thing for certain games, its not policy yet so until it is, they will get my gaming dollars.