I enjoyed MK7 more then I did MKWii :V
Main reason really was that the default item system I found much more balanced, plus the addition of gliders, going under water, customization of Kart bodies, gliders, wheels, etc. gave it something quite interesting. While Wii's have probably the worst usage of the blue shell and the bikes were clearly better then the karts in most occasions. (Like you're almost always a nervous wreck because of the Blue Shell when you get to the 3rd lap, at least in MK7 if you look at the bottom screen you can see a blue shell coming before it hits you. You can then plan much more accordingly to either take the hit leaving your defensive items behind you, or try to screw with 2nd place by either letting them pass you before it's launched or take a kamikaze that hits both of you.)
Mario Kart 8 seems to combine the best of both games though. So I'm happy about that. And the Bikes are much more balanced as a result.