you just cant be serious in thinking MK64 is better than MKDD or any other MK for that matter. MK64's tracks are far too long especially considering how slow the game runs, nulling the sense of speed. The AI of the computer players is just too simple (stick as close to the leader as possible unless they ge smashed by train etc), it just isnt frenetic as SMK, MKDD or MKDS.
At the time of its initial release, I considered MK64 better than SMK (through £39.99 rose tinted specs), but 20/20 hindsight changes that. Sure SMK has aged condiderably (nigh on impossible to just jump back into -unlike n64 counterpart) but still has that racy feeling (again unlike n64 counterpart).
The GBA mariokart is similar to SMK but has now been overshadowed by the awesome DS version ( try 8 players in a room racing, unbeatable) which has retro tracks from all the other versions.
MKDD is playably, graphically and overall more substantial than MK64. Yes the player switch thing can seem to be superfluous at times but it cant be all bad if the concept was "borrowed" by kart racing competitor Crash.
The GC version retains all the freneticity of SMK with the 3dness of MK64 so no contest - apart from MKDD v MKDS?????