8(D) > 7 > Wii

Mario Kart is just the kind of series that gets better everytime. However, I did play MK7 much more than MK8 + MK8D (it's actually my most played game of all time). So I do have a stronger personal 'connection' to that game, even though I know it's not better. If that makes sense...

In the next game I'd like to see the feature return in which you could race against seven ghosts of other people in the time trials. I liked that a lot in MK7, it was a great motivation to try to beat my own (and other people's) best time.