Personally, I was a fan of free DLC when buying new copies of games. The used gaming market is good for everyone, I believe, and this method rewards those that buy new games. I bought a lot of used games in the past because they cost $15+ less and the new copy rarely offered any additional incentive... maybe an instruction manual? I was never a fan of having a code to activate a game though. Gamestop would just start even paying less for the games, price them slightly lower, and then offer a scratch-off code along with the used copy.
In the end though, I think within the next 5 years, this used games for current titles will be a thing of the past for one very good reason: the internet.
I recently moved to PC gaming. In roughly a year, I've racked up over 200 games (some big names, some indie, some freebies, etc.), but I never bought a single physical copy of those games. I think consoles will move in this direction. You can already buy/download games online, but it's still much more common to buy a game disc. Internet speeds and bandwidth are increasing (slowly around the US, anyway) and a huge majority of console owners already have internet, making this a viable system. I don't believe the physical disc will be eliminated in the next 5 years, but there will be a huge shift to digital copies.
Steam's console probably won't be a huge success, at first, but I do think it'll have a substantial effect on how consoles are done. Developers will notice that every person that buys a digital copy will mean possibly one less "used" copy and in order to shift everyone to buying digital games, we'll start seeing more Steam-like sales for digital content for all systems. Of course, not everyone can afford internet or $60 games and many people see no reason to keep a game longer than it takes to complete. The first group is why discs won't be eliminated for a long time. The latter group - those that really drive the used gaming market - might end up being constantly hassled over the next few years by bullsh*t policies and a majority of them will be picked up by Gamefly or some sort of temporary gaming service.
Overall, I think used games is a very small problem. DRM, bootleg copies, and pirating is a much, much bigger issue in my opinion. Many companies probably believe the solution to this is exactly the same: the internet. As we've seen though, everyone seems to hate this solution. Diablo 3 launch was a disaster, I haven't been hearing anything good about the new Sim City, and Ubisoft has already backed down with their ridiculous DRM system.
Also worth mentioning is OnLive and that new nVidia grid service. These eliminate the need to download/install a game, imposes DRM (since you don't actually own any thing), and removes the physical copy so it can not be resold. I don't know if this type of system will become popular among gamers (I don't care for it), but it certainly is another direction gaming could take in the years to come.
Edited, Feb 4th 2013 1:15pm by xypin