Not exclusively but it will be a big marketing factor. The main deciding factor will be the possibilities the consoles offer and how developers use them.
I've played with Kinect a bit but found it too unresponsive and imprecise to truly captivate me but the groundwork was laid. I'll be curious to see the improvements of the 2nd generation and the same applies to the Playstation.
In order to have these high grade add ons work you need new hardware and these may become the factors deciding the race or it will roughly level out again with no decisive winner.
Wii was such a smash hit because of the motion controllers.. have you ever been in a room full of mid 20s and mid 30s people who are having a blast while bowling on a console? That was an eye opener for me and told me that with true mainstream gaming you need innovative ideas to engage people and i believe MS has the upper hand in that with their Kinect system (though Sony tried to catch up).
However having shiny, state of the art HD graphics are a necessity nowadays with the prevalence of HD TVs.. i was kinda disappointed with Halo 4 when i played it on my big TV because developers seemed to have reached the limit of the old generation hardware.