The opinion of used over new games isn't the best topic to debate. Preference is based on the type of person the user is.
If you're like me, you like having a:
brand new and shiny
game, and being able to unlock all of your achievements/levels, and still have the evidence right there on your bookshelf. Since you're not renting, you're able to play it for years to come. It's also a fun experience to wait in line for Gamestop or Target to open, and for you to rush in and get your hands on a fresh,
clean copy of the game you've been waiting so long for.
Another person could say that it's fun to go to Gamestop and rummage through the big bin of game cases, and play games just for the hell of it without spending the full price. If you're renting the game, you also don't have that dead weight of a case cluttering your room, when you could just return it.
The argument is very easily biased based on personality, and there's no right or wrong side of it.
EDIT:
-snip-
Then again, you do have a really good point...