Windows is used over Linux because, lets face it, Linux does not have the awesome applications such as Office, Counter Strike, Photoshop, etc that Windows has. Even installing Java on Ubuntu Linux can be a headache for those that are not tech savvy. So for now, we believe that Windows has the upper hand in the OS battle in terms of desktop devices.
But what about mobiles and tablets? This is where things get interesting. Windows does not have the upper hand in mobile and tablet devices as iOS and Android dominates that field. Believe it or not, iOS and Android are actually partially based on the Linux kernal in some shape or form. Does that mean that over 95% of mobile devices run on Linux? Technically, yes. So there you have it Linux fans, you guys are dominating in the mobile niche.
OSX, on the other hand is not a very preferred OS when it comes to handling technical aspects of computing. The only reason why many developers use OSX is the ability to build apps for iOS, which is also ironically based on Linux. Besides XCode, from OSX, we do not see any other reason to use a Macintosh device running OSX other than its aesthetic appeal (we admit, macs and their OSX do look pretty good!).
So there you have it, our opinion on which operating systems are the best/dominant for whichever devices you may use. Windows for desktop, and (Android and iOS) Linux for mobile.