The issue of used game sales has been a hot topic for a while, with online passes and DRM stepping in to try and prevent resale. Publishers want to sell you a brand new game, and while console gamers can always buy used if they so choose, PC gamers are pretty much restricted to new copies. That may soon change, as the European Court of Justice has ruled the resale of digital software cannot be restricted by the creator. This basically means games bought digitally can be sold to someone else instead of staying with you forever. This is just a preliminary ruling as a national court has to enforce it, but it is a step in the right direction. This ruling is also about Oracle's tools and not games specifically, but it can be applied to the latter.
Selling DRM-free games should not be an issue provided you permantently delete the original copy off your system, but games that have DRM are a bigger problem. The European Union does not allow DRM games to be resold due to anti-circumvention rules. The kicker is forcing all games to have DRM would be against this preliminary ruling since it restricts preventative action, but the courts would need to be sure the DRM is not there just to combat piracy. It will be interesting to see what happens in the long run with this ruling and whether it comes to pass. I imagine digital game and software stores will fight it as much as possible, so we just have to see where it goes.