IMO Kinect sold well because of hype, this usually works especially well for the United States. A strategy Microsoft seems to have been perfecting over the years and they understand the weaknesses of the US consumer second to none.
You also saw this with Halo 3, a short game IMO not much of a challenge to finish, graphically underwhelming and a non-default online multi-player you as well as all your gaming buddies have to pay extra for each month/year. Still it got near perfect reviews from the US media, this while it was clearly very far from a near perfect game.
Similarly Kinect was hyped by especially the US media when Microsoft revealed their fake Milo demonstration. I myself also complimented Microsoft on its achievements not knowing at the time it was just a cheap fake. Regardless Kinect/Natal got so much overhype, beyond believe, hyping it as the "future ", revolutionary (Milo) and the next most amazing thing in gaming. That's why I stated back then, many months before Microsoft actually launched Kinect it was already geared towards commercial success (despite I already knew it was predominately based on a fake demo), because of the massive overhype by especially the US media and 360 fans.
Kinect of course isn't the future, but of course, just like Kinect and Playstation Eye (as well as Nintendo Wii / Playstation Move) are inspired by pioneering through the Eyetoy (remember minigames such as Eye Sports, Eye Play, Kinectics, etc), there will some day be products which include Kinect-like features, but actually works as advertised.
Here in Europe Kinect has been much less successful and as predicted is a non-factor in Japan. IMO the Kinect hype will not survive until next holiday season.
