IMHO the problem with MK is that it relies far too much on gimmicks than pure racing now...
SNES MK was the best because you had to use the course to your advantage.. save mushrooms to take big jumps... turn accurately to maintain speed... Feather for short cuts... The breaks make a huge difference to taking a tight turn... No lame cheap weapons repeatedly occurring (getting a red shell was hard work.. and you had to save it for the right time)...
MK 64 started the whole trend of "excessive items and gimmicky snaking" - it really took the fun out of the pure racing bit... Since now there was less reward to actually learn how to exploit each angle of the course (since one missed snake or three red shells could f*** you over)...
GBA MK was ok... but nothing really new... It also lacked the excellent physics of the SNES version (it was really kinda strange overall)... Overall pretty dissappointed as it was relatively uninspiring (the new battle courses were pure suck)...
DD was atrocious... I don't know what the hell happened... I think any idiot can win in this game... It definitely does not reward skill... stupid luck is more likely... And the sad thing is that the gameplay itself is *very* shallow... You can only do so much before you realize that the game is gonna screw you over...
DS MK... IMHO this just continued the poor tradition of MK64..
Mario Kart GP... I actually liked it because of the pure racing... get rid of all the lame excess items tho... Add in more depth to the courses... We might have a winner....!
Mario Kart GP 2... Remains to be seen...