Mario kart 8 because it has a much greater WOW factor than nsmbu.

And a lot of people who aren't very into mario kart seem very excited by this one.

I think they will be around the same sales in the end.

MK8, because there's demand for it and Nintendo will surely bundle this game next year or something.

As (I believe) everyone else has said; MK8 will sell the most. It's just a bigger seller, particularly when it inevitably gets bundled.

This man is telling the truth kids!

on topic: Mario Kart without a doubt. Dem mass appeal will drag everyone into it.

Easily Mario Kart 8. NSMBU's 5 minutes of fame are over!

Def Mario Kart. MK is a huge GP game. More so than regular Mario games.

Mario Kart since it will most likely be bundled.

MK8

Has a broader appeal and will drive sales where 2D mario seemed too similar to NSMBWii to do so. (granted it was a lot different / better, but peeps only see the similarities) Hello whole WiiU seemed too similar to Wii for peeps to see it was a new console.