Man, you pepole just don't realize it.

It's not the motion controls by themselves, if it weren't for clever marketing that made the users think the motion controls are better than what they really were at launch, affordable price, and the early support of Nintendo loyalists, the Wii would've never gotten(?) as big as it is today, even with Wii Fit.

The Wii also sells extra because it is the most known/famous of the three consoles, the biggest ones always sell extra because they are just more known to the common public.

To prove my point, take the PS3, make it 300$ at launch, give it amazing marketing, take out Blu-Ray, leave the HD graphics intact, and give it the same games.
Would pepole say that it sells well because of the graphics? Because of the games? No, pepole would've said that it sells well because of the brand name and stuff like that.

Umm... Mario Kart uses Motion Controls. At least that's how the truely hardcore use it.

OT:

It definitely contributed a lot, but it was mainly the games that used the motion controls correctly.

The success is less about motion controls than people think. As has been mentioned, two of the Wii's most successful titles, NSMB Wii, Wii Fit, don't even really use motion controls. The root of the success is really having new ways to play games, and appealing to non gamers and ex gamers with accessibility and pure raw gameplay, something that the HD consoles don't really accomplish. The motion controls just helps enable this accessibility and uniqueness.

5% motion controls

95% games that used motion controls

Honestly it's like asking how long is a piece of string, there is no definitive answer.  When the system was released there were so many other factors in play you can't possibly hope to quantify it in any meaningful way.

It's the same as asking what would have happened if the PS3 wasn't $600, the Wii had released a year earlier the 360 didn't have the RROD? The short answer to all questions is they would have sold more but we can't possibly hope to quantify that. 

So to answer the question, of course it was a factor in the Wii's success, how much though is anyone's guess and nothing more.

The Wii's success is due in large part to the fact that it has a steady stream, a strong standing library of software that appeals to all demographics.

This is pretty much it.  Implementation is the key.  

Same story for DS.  Games sell hardware, features are just there to support games.  The sooner Sony & MS figure this out, the better off they'll be with their Wii-too frankenstiens.

Wii Sports:

If the Wii had been bundled with Zelda and Zelda had been heavily advertised with it's motion controls.  Would the Wii really had the incredible sales when released in December 2006?

Without the motion controls the Wii was a minor upgrade to the GCN which was the 3rd place console.  Wii stormed out of the gate not because WiiSports was awesome software, but because of Motion controls and nothing more than a decent demo pack (WiiSports) to promote it.  WiiFit kept up the momentum and look at Wii now for every Wii that sells .5 WiiFit sells.  This isnt coincidence and it isnt the software it is the idea of burning calories while playing.  Moms dig it for themselves, and Moms are scared of video games making thier kids lazy and fat.  Motion controls and WiiFit alleviates that fear. The core Nintendo titles have come along for the ride.  Face it and get over it.  Motion is what made the Wii. 

As for my signature that is what I believe. I dont believe individual titles push things much other than temporary blips.

Sorry, I'm just going to continue to assume that you are being enormously witty during this whole thing.

Ho ho ho ho! You almost got me again!