I did not take good care of my boxes, so there's not much worth keeping. Also, a lot of my "boxed" games came from the used section of EB and Gamestop, and they just put everything in plastic bags, minus boxes, at the time. You can still get boxed games in good condition at Half Price Books, though not as cheap now since they started looking up the dollar values online.
I don't have a lot of games on Steam or GOG either, because I tend to finish the games I buy before getting new ones.