All the games Mr. E said. Those have to be my all time favourite games, especially Paper Mario. If you still have your Nintendo 64, get the original Paper Mario too. Also, EVERY Gamecube owner NEEDS to play Resident Evil 4. The graphics, cutscenes, music, and visuals are all jaw-dropping.
A couple good ones are LOZ: Ocarina of Time and LOZ: Wind Waker, SSBM (Super Smash Bros. Melee), Resident Evil 4, and if you're into cars, Need for Speed: Underground. All the others I can think of usualy fall under people's "Bad Graphics"/"Bad Storyline"/"Bad Controls" categories...
my all time jams: metroid mario tennis (need baseball now) animal crossing super monkeyball