MK Wii being severely underrated here
Huge assortment of characters, tons of unlockables, actual online play for the first time, first game to have motorcycles I believe, fun control system (I loved the wheel)
I'll only list the ones I have...
MKDD - great concept with two racers and unique items. soooo many memories playing this game with my brother
MK Wii - reasons I listed above
MK64 - classic... not else much to say
MK 8 - great gameplay, but the lack of unlockables kills me. still fun to play with friends but not much reason to play on your own
Just a further note on MK8... Nintendo seems like its really watering down its games knowing that kids will be playing them. No unlockable characters or maps in MK8, no unlockable maps in the new Smash game and the characters you unlock are just at random and not for anything actually challenging. This combined with the lack of a universal achievement system (like Xbox or like trophies on PS4) just make the games feel pointless sometimes. Unlocking random wheels or gliders in MK8 is really crappy motivation, and again it annoys me that you just unlock them by seemingly picking up coins during races, not having to do challenges like beat all circuits on 200CC or something like that