Rayman 3 - Deserves any platformer fan's attention. Also available on the Rayman 10th Anniversary double pack (which also includes Rayman advance, which is an excellent port of the first Rayman game).
There's more than one game called Rayman 3, isn't there?
I heard the Nightmare Before Christmas GBA game was pretty good.
"There is much pleasure to be gained from useless knowledge." --Bertrand Russel (attributed)