People who are ignorant of technology and computing think that windows is the only or the best operating system around.
Many people who are knowledgeable of technology and computing think that Linux is the best operating system.
But its the people who had experience with all, that realize that Windows is still a way better OS than Linux in many ways despite its shortcomings.
The fact is that Linux is no good in its free software form. Commercialization is every much required to make it any good for serious use. Most of the companies that use Linux either buy commercial enterprise versions that cost a bomb because of the support and maintenance they provide or alternatively, the company hires experts to take care of the maintenance for them for heavy pay packets. Other than that, the only people who are using Linux are the ones who either want to experiment with it or have so bare min requirements that the components they are going to use are stable enough for daily use.
I have myself been trying/using various flavors of Linux starting with Slackware Linux 2.0 in 1997. Most of my B.Tech Course work involving programming was done using GCC under Linux. I used to have 4 different flavors of Linux on my machine during my college days and I still have the latest versions of Ubantu and Mandriva distributions installed on Virtual Machines through Virtual Box. I agree Linux has come a long way from where it was once, but believe me, it still has a long way to go if it has to be any serious competition to the likes of Windows.
As for windows, at the cost of some stability, it bought ease of use, compatibility and acceptance. Something no other OS was able to achieve even though many were around for as long as windows did. Software written 10 years back still works on windows. This was because, MS always ensured that their backward compatibility is maintained. This is indirectly a reason for the less than perfect stability and security of the OS. Though MS has done a lot towards increasing security and stability, it does not do it at the cost of loosing backward compatibility. I would go as far as to say that they have been doing a decent job of balancing both. A major part of the problems with Windows is because of bad code written by Third party application/driver developers. They made it so easy for even the developers to write new apps that developers keep doing sloppy work leading to the poor stability of the OS.
On the same lines, Mac OS is the exact opposite of Windows. Apple has been doing a very sloppy job with its OS and its the third party developers who ensure that the OS bugs do not ruin the experience of the software they developed. they do not care about backward compatibility or stability of SDK's. Its a major pain for any medium to large developer to develop for the OS and keep releasing patches every time apple breaks their frameworks. That's why you don't see a lot of developers seriously developing software for this Platform.
As for those Linux and OS X fans who diss that MS has been nothing but a copy cat, even Linux is a copy of Unix and all other Unix clones that came before it. Mac OS is no better. All the so called Apple introduced concepts were copied from some one else. So why the special treatment for MS? The only reason I can come up with is that people like to support the underdogs.