@Avinash and Metallicube:
I don't and cannot expect from Sony and MS a fully working reaction to WiiMote and its philosophy, if only because they can't seamlessly glue completely new controls and gaming philosophies to consoles that were born completely different and "classic" and have now accumulated tens million HW and SW sales without these novelties. I expect more that for this gen they experiment with the new devices and dev tools, but a true complete and effective reaction will be possible next gen, including all the novelties in the standard equipment, possibly inventing something new or also, like I wrote, choosing a mix from the new and old things that they think could differentiate them from competitors and cater for audiences partially and not totally overlapping. This gen, necessary experiments apart, they'll do at most damage control, never tried to deny it, what I believe is that despite Nintendo being the undisputed leader, MS and Sony are reacting well enough to avoid disruption or delay it enough to be ready when next gen begins, nothing to write home about, but enough to prevent Nintendo from reaching 50%.
How well MS and Sony will do next gen, though, is a thing that we can't know now, but nothing is granted to the previous winner, and both Nintendo and Sony know it perfectly because they experimented it.
And in previous posts I didn't even mention XB360's tie ratio a lot higher than Sony's and Nintendo's, so that Wii SW % Let's not forget that failed invasion of Russia through the centuries show that slowing and getting in the mud fast intruders/disruptors is an effective tactic to stop them, despite it being completely different from counter-disruption.
And then there is another factor: de facto synergies, even unintentional: Nintendo and MS de facto effected a synergic action to dethronize Sony, but Sony and Nintendo did and are doing the same to prevent MS from conquering another monopoly and Sony and MS are doing another one to prevent Nintendo's disruption. With 3 strong players balance is a lot more complicated than oversimplified theories. Even without considering 3rd parties that furtherly complicate all.