If you can find a copy for less than $100, get the Metroid Prime trilogy. Xenoblade is another good call, but you will have to drop another thirty bucks on the classic controller for that to work (I've been told it doesn't work with GameCube controllers). Super Paper Mario, Donkey Kong Country Returns, and Skyward Sword are also highly recommended.

Or just get Paper Mario: The Thousand Year Door and play the best game Nintendo has made in the past decade.