Should Nintendo drop game prices after they been out a few years?

A few days ago I went to gamestop, My plan was to get my little cousin Super Mario Galaxy for her birthday. Her family got a Wii for Christmas and I want to introduce them to some good Nintendo games. I found super Mario galaxy, and it cost $35 used and $45 new. I have had always had a problem (and thanks to formspring, you do to) with Nintendo not dropping prices on games that have been out a few years. I have passed on some DS games hoping they drop in price, which they have not. I'm not paying 35 bucks for Mario kart DS when it should only cost $15 by now. This is only hurting Nintendo by not allowing there games to naturally drop in price, like all games do. Nintendo should remedy this problem by the the next gen or consoles, stop it from becoming just another reason Nintendo is number 3.