[quote name='Zon27']You should be able to. Gamestop's rules now apply. Their rules have always been 7 days, if you don't like the game or beat it or get bored with it or decide you didn't like the price, etc you can return it for a refund within 7 days.[/QUOTE]
Unfortunately, this seems to be YMMV, at least for me. Gamestop's rules may apply, but my local EB's say they don't, so you break the seal and you're stuck with it.
Chances are, if the OP's EB's are still putting seals on the used games, they are still going by the old return policy.