Games like Mario Galaxy stay desirable and hold their value.
There are still some games to look for on the Wii for cheap. Galaxy Wars, Monkey Ball Banana Blitz, Zack and Wiki, Boy and His Blob, Lost in Shadow, Mercury Meltdown, Elebits, Excitebots and Excitetrucks, Madworld, Blast Works
I dont understand Nintendo's pricing policy in games over a year old. I think it would more logical to price them lower to encourage impulse buys. Another thing is a higher price someone may not purchase an old game from a series they haven't tried before. There are plenty of franchises that I was unwilling to give the first game a try until the price was really low. If the game was good than the future titles I would buy when they come out.