DS = DD > 7 > Wii > 64 > SC > MK
It's hard for me to choose between Mario Kart DS and Double Dash. The DS version was great because of all the awesome courses and online play. Double Dash felt really smooth and I loved switching between two characters with unique items. Seven is pretty good on a technical level and it's a lot easier to follow than Wii, but it feels kind of souless to me. Wii is just too frantic. The courses are huge and I don't like the bikes. 64 is good for nostalgia and gave the series the Block Fort. Everything else... not much of a fan.