Yes, AFAIK.

On a aesthetic level you would think Mariokart would easily win. The game is more casual friendly, and has more variation in play. Unfortunately each generation Nintendo has shown that it gives less then a rats ass when it comes to the series quality. You often get the feeling that they do just enough to sell the game, but not enough to make it positively glow. They are stingy with their track allotment, and the battle mode arenas well there is just no excuse for merely four. Basically I do not have high hopes for the next installment unless Nintendo proves they are serious about giving the game the kind of love they give their other series.

Further more I think Smash has an unappreciated advantage in launch window. More specifically the lack of competition on the platform when it launches. Thats where Mario and company can get squashed. Smash will be the game of the moment. Were Kart to arrive in the late fall or even the holiday season it would face a tougher market. One where the consumer isn't quite so starved.

Yes I think that the head start will help Smash enough to win. Right there for starved gamers at the right time with no competition, and further more its legs will have a lot more room to work with. Kart would be really lucky to catch up. I am not just thinking of dedicated Wii owners here either multiple console owners will have a lot to choose from by the time kart arrives on the scene.

Launch window and Nintendo neglect probably seal the deal. However I will say this I do not think either series will not put up the numbers some posters expect. Wii either title appeal to ultra casual player? What will the effect of other Nintendo offerings be. We do expect more then two heavyweights from this year right. What effect would another Zelda have, a Donkey Kong, Disaster, or Starfox have on the situation. Regardless those would do more harm to Kart then Smash. Since none of them will be around when it launches.

I think Mario Kart Wii will win, but the sales for both will be phenomenal.

Mario Kart Wii: 15+ Million
Super Smash Bros. Brawl: 13+ Million

 Very good point. I was thinking MK before but if neither's bundled it'll probably be Smash Brothers.

brawl will sell same amount as mario kart

I think MK will appeal more to casual gamers as myself. Then again, I never liked the SSB series so I'm biased that way.

Anyone actually thought that MK will also give you the option of using the GC controller?

Yes they are inferior. They make far more difficult to make precise adjustments to a trajectory compared to using a joystick. This is because of the way an accelerometer works.

Basically, an accelerometer consists of a chunk of material that is free to move and some electronic circuitry to figure out how fast it moved, and in some cases, in what direction. ^{see wikipedia}

Unfortunately, the human hand is not very steady from a computer's point of view. This results in wild variations in the data being read by the accelerometer. Because of this, the controlling program (a game) has to be able to compensate for this. In other words, the computer has to guess which movements were intentional and which were accidental. The only convenient way of doing this is forcing the computer to update the acceleration data at  a relatively slow rate. This results in an apparent unresponsiveness, especially when compared to a joystick.

That being said, I will have to agree with what was pointed out above, i.e. it is subject to personal opinion whether or not a motion sensor is good or bad.

Like MK:DD outsold SSBM on GC, the same will happen on Wii, but both will sell way more copies thaks to Wii's popularity.

As for motion control, Mercury Meltdown allows very fine control with the wiimote. It's very sensitive and responsive. In most developers hands I might be inclined to agree analog stick would be better, but this is Nintendo on one of their flagship titles on their own console. I expect it to rock and even be considered superior to analog.