My vote goes to San Francisco Rush 2049.
Add in online play for multiplayer (16 players on stunt tracks, 4-8 for races) and a light graphics overhaul and this game would be hella fun.
Already mentioned in this thread but definitely needed:
Chu Chu Rocket
Jet Grind (Set) Radio
Pac Man Vs
Conker's Bad Fur Day (just original multiplayer w/online would be sweet)