First, I am not saying that used games are the devil and should be abolished. Used games are all right and I see nothing wrong in them. I don't think they are killing the industry or anything. I do understand why developers and publishers want some money from used game buyers, specially to access services like multiplayer servers (because they are a service) and try to capitalize over the used games with DLCs.
But I also don't see the big advantage in buying used. Even if the game does not have DLC or an On-Line Pass, they are hardly a better option than new games. See, I regret trading all games I have traded. It is not a question of missing the games that much, but the fact that the money I saved was not worth getting rid of those games. A $60 game will be trade for $30 or less, depending on how rare the used copies are and how much demand there is for it.
And if I use the credit to get another used copy. they will vary from $55 to 40$ if it is a recently title (less than two months). And if I wait more, the chance is the game will go on sale, and a new copy will be selling at the $40 price after three or four months, with used copies selling around $35~20. So, I see no advantage in buying used anymore.
Unless it is a hard to find copy, either new or used, the monetary advantage of buying used is lost in a few months. If you wait enough, you will buy the game at discount, new, with all DLCs bundled and on-line passes. If you wait for a Game of the Year edition, you get all DLC free. And there is the Platinum/Best hits series that allow you to buy new copies for cheap too.
So, if you buy games used to save money, you can save the same, sometimes more money, just waiting for price drops and cheap reprints. I got The Saboteur for a third of its price this way, brand new, Fallout 3 with all DLC and half price in a Game of the Year Edition and Dead Rising 2 new for half price. And many on-line retailers have discounted prices after a mere weeks of a game hitting the shelves. Unless you are in a hurry to play and want to save a few bucks, the best option for both gamers and the industry is to wait for the price cut. The used market as it is today save very few money for the gamer and make GameStop and its likes immense profits from this.
The retailer will profit from the new copy, and every time they resell the game too. Nothing wrong in itself, as there is nothing wrong with used games per se. But I prefer to know that the ones who made the game are receiving part of my money and not just the guys selling it.
I will not say that gamers who buy and trade used games are wrong too. Everyone have their problems and sometimes saving that little bucks can be a need. I am suggesting to them, tough, that there is options that are more worth, if they are in disposition to wait. You could say that you cannot wait, because the game will be beyond spoiled after a few months, or that the multiplayer will be deserted. But if the game you are looking for is so good and so worth playing as soon as possible, why it is not worth the full price? If you cannot wait new copies to price down, I think the game may be worth brand new then.
Think about it. Why are you buying used? Can you wait for a sale? Maybe if you think about it, new games will looks like a better option than used ones.