Why? Because Mario Kart appeals to a more diverse range of people.

Mario Kart will get girls.
Mario Kart will get the new expanded audience with the free wheel and easy controls
Mario Kart will get the casual because it's always hell popular with a broader audience.
Mario Kart will get all of the core because it's Mario Kart and it has online play

Smash Bros will get the core because it's Smash Bros and it has ZOMG11!1!!!!!timesONEMILLION content.
Smash Bros will get some of the casual because it's such a cool concept.
Smash Bros wont get girls, they don't like fighting much
Smash Bros wont get expanded audience because it's too complicated.

In the long run, Mario Kart will far outsell Smash Bros.

I'll put a bet on it :)

I agree. Brawl will have a huge debut with decent legs. Mario Kart will have a decent debut with huge legs. Mario Kart should overtake Brawl in the end.

I too think Mariokart will outsell Brawl, but not by much. Both will sell over 10 million though, joined by Wii Sports, Wii Play, Mario Galaxy, Wii Fit and Animal Crossing.

I agree, but MK should be GC controller compatable to get more hardcore, like the ZOMG hardcore. ;)

Mario Kart isn't getting me, that's for sure. Brawl is, though, mainly because of PIT.

makes sense,
Agree too, Mkwii would sell more

i know some hot chicks that play smash bros

I'm not sure, I don't know if MK will or even could have the opening that Brawl supposedly had in Japan. I mean it seems close to over 1 million in a single week, which is ridiculous. If thats true, it could probably push 2.5 if not 3 in Japan, and combine that with what should be very strong sales elsewhere, I think Brawl might have the edge.

OriGin, your points make sense...after all, Mario Kart is pretty much the only game the ladies play...even Double Dash.

But honestly...I have yet to see any polish from Mario Kart...any sign that the game will WOW me.  It kinda looks like a GC game to be honest, but that's off the few screens and videos we've been given, and I'm sure it's not the final build.

But SSBB is EPIC.  It is nearly perfect.  It is being hyped like no other game...I do honestly believe this game is getting talked about more than the Halos even.  And it could appeal to the expanded audience a little...the game is "complicated" for people that don't know much about videogames...but with the Wiimote only controls...there's not much to learn...just use the D-pad and mash the 1 and 2 buttons...it can't get much easier.

I'm basically saying that the hype and perfection of SSBB + the possible flaws of MKWii might keep MK from selling more.  

The huge casual audience will LIKELY push MK past it...but we'll see.

I think Brawl sell more than Mario Kart, but for a little.