64 runs on nostalgia, really. I loved it as a kid, and it still is good, but I'd say some of the later ones are objectively better. I enjoyed the DS one, even if the drifting was horribly broken. Mario Kart Wii is probably the one most people are familiar with, and it is good. But I really enjoyed Mario Kart 7, it added some new things like the gliding, that didn't detract from the racing itself.

I haven't played 8 yet, so I can't really comment.