Another factor to keep in mind about used games is that many people only tolerate the $60 price for a 10 hour game because they know the game still has value when they are done with it.
You know you can trade it in for $25 or sell it used for more, so the initial price is not bad. As soon as games have limits in trade-ins, (digital distribution) people will be less willing to spend full price on a game.
The other problem I have is that games stay at full retail price for way to long. A game should be full price for maybe 3 months tops. The fact that some year old games (or 3 year old in the case of Nintendo) are still full price at retail is part of what is driving people to buy used.