The point's been made, but introducing a bunch of software to go with the things is key. Microsoft and Sony are in a better position to do this than Nintendo because they're apparently more willing to subsidize third-party development than Nintendo and because they generally have better third-party relations than Nintendo (mostly due to Factor #1).
By contrast, Nintendo pretty much has to work alone, which means less software (especially since they're a relatively small company that's juggling five different platforms right now). So Motion+ isn't going to get the support it needs, while Natal and the Wand will. At least at first. To be honest, I don't see either as being a long-term success right now. But then neither of them have showed their cards yet.







