This is an odd question.
Windows is not a monolithic operating system, – there are at least three variants in wide circulation at the moment – XP, Vista and 7. The same is true, to a lesser extent, with Apple’s operating systems. However, MacOS represents closely-related variants of Apple’s proprietary Unix.
“Linux” should not be conflated with “operating system” either – it is a veritable menagerie of operating systems running on everything from supercomputer clusters to cable desktop boxes to phones (Android). Linux is itself a Unix-impersonator (or derivative, depending on your point of view)