Rather than list the same ones as everyone esle I'd like to recommend two under represented classics.
DK Jungle Beat- Single most original thing to happen to platform games last gen. It's so intuitive and fun to play a side scroller with bongos, I dare you to play this all the way through acheiving the highest level trophies, it's amazingly well designed.
Warioland- Created by Treasure, this is just one kick ass fun platform/brawler (amazing game throguhout with the exception of a really weird end guy).