Mario Kart 64 was my 2nd favourite game on the 64 (after Smash Bros) and the DS version barely left my DS till I got it chipped.
The Wii game while damn fun in multiplayer and multiplayer online, is annoying to unlock everything. I've actually stopped playing as I find no enjoyment on the Bikes or the 100cc class that forces me to ride them.
I'm sure I'll get back into it sometime, just not anytime soon.