I support this if done correctly which can be guaranteed that Activision won't. Imagine selling a game for $30, and then having the second half of the game downloadable for $30. That way the player gets to taste the game and see if they like it enough to keep paying for it. You know that Activision won't be that creative though. They will just keep charging $60 for their games, and then ask for another $30 for content that should have been part of the game to begin with. As an added bonus, a $30 game isn't going to reach the discount bin very fast, and DLC never needs to see a sale. They could rake in the dough because people are willing to nickel and dime themselves if they like what they are getting.
Honestly though, I think Gamestop takes a percentage off of the retail price when they resell, so if they start pulling only $3 per new title instead of $5, they are going to have a much harder time keeping in business as people aren't going to be willing to buy used if there is such a marginal price difference.
I'm looking at this purely from a dev's standpoint. As a consumer, I prefer the option to pay as little for the most I can get, so the only way I'm ever paying $60 for a game is if it's the collector's edition for a game I really want/love. Used games do give me this option. The only caveat I have then is that I buy my games to support the devs. Otherwise I may as well just be a dirty pirate and loot and plunder without regard to who I'm hurting. At least then my wallet will be heavier.