Of course they're proper operating systems. People who want to defend Windows like to say this, because that makes them feel better... I guess. After all, it's Microsoft themselves that kind of begged the question, with Windows 8. They thrust this WinRT/Metro tablet OS in every desktop user's face, and said "this is the future". They even started calling that subsystem "Modern" and the old, desktop-class Windows "classic" or "legacy".
Microsoft messes up every other version of Windows and then the next version is a fix. They have spent a lot of money shoving the Windows 8 disaster down people's throats. The software business is under attack from free office applications, Google and the move to mobile. Microsoft has messed up the XBox also with being "arrogant controlling jerks" and is losing market share to Sony with this round of consoles. The Nokia buy of last resorts to break into the mobile market has already seen sales fall and is looking more and more like another disaster.
Apple could give away or nearly give away their Mac OS X and probably put Windows out of business on the x86_64. Apple already announced a free upgrade for OS X which is a savvy move. I don't know how much the Justice Department would put up with a price war and Apple may be content with the higher margin sales for OS X. Apple has missed the boat by being too closed and their Apple TV should have been better with games to take some market from consoles (it may have required staying with x86_64 instead of ARM). Apple does understand the importance of economies of scale and vertical integration where they have stealthily become one of the most advanced processor manufacturers. They have bet on ARM so the question is how far can ARM go in performance? There is a big gap between the power efficiency of ARM and the performance of x86_64. The A7 going 64 bit is a bit of a compromise for this problem as it's not beneficial for a phone (even if they say it's up to twice as fast) but they can use it in other devices like iPads and laptops where it may be an advantage. The new AARCH64/ARM64/ARMv8 ISA has advantages but going 64 bit can waste a lot of cache as this is now another 32 bit fixed length RISC encoding with a little better code density than 64 bit PowerPC but not as good as x86_64. It needs 50% more caches than a 32 bit processor designed for maximum code density (and better than Thumb 2). Remember how small the 68k Amiga executables were and how much memory the AmigaOS used? Now think 5%-15% code density improvement for ISA and ABI changes and another 10%-20% for better code optimization. Now throw in 1-2 GB of memory for modern hungrier applications. Do you think such a modern enhanced processor with an efficient OS like AmigaOS could compete with the 64 bit mobile devices that went "big"?
Truth is, all of Windows is getting their ass kicked by Android. Yes, that's in units, not money. But the real strength of an OS is only one thing: the applications. We Amiga users ought to grok that... doesn't matter if your OS is better, only what you can actually do with it on a practical basis. When you look at those numbers, it's easy to imagine that the mainstream of software support will move away from Windows.
I think a lot of the reason why the applications are doing so well is that Android is so open. Android is less efficient and optimized than iOS. How fast can executing byte code in Linux on a portable device be? Perhaps a more efficient but also open OS could come in and displace Android?
These numbers also suggest that if Apple could bridge MacOS and iOS in some way, making it more of a situational thing than an OS thing, the desktop-vs-mobile question, they could be just as powerful as Microsoft, at least numbers-wise. And if they respect the desktop model, rather than ignoring it as Microsoft did, they'll get desktop converts, not simply "iPhone coattails" buyers of the desktop systems. MacOS and iOS are, of course, both built on "DarwinOS", which is just the BSD UNIX bit mixed up with CMU's Mach kernel (plus decades of Apple tweaks) and NeXTStep. This may not be on supercomputers, but it's just as much a desktop-level OS as Windows.
I think Apple has partially bridged the gap between Mac OS X/MacBooks and iOS/iPhone/iPad. They have transfer/synchronization programs and there are several "familiarities" between them. I wonder if they are trying to strengthen ARM to eventually replace the desktops and MacBooks with many core 64 bit ARM processors. They may be able to move to one consolidated more flexible common OS with different user interfaces for different purposes in the future also. I don't know if battery technology can keep up to feed the mobile devices to desktop like performance which they seem to be gambling on with ARM64. Also, when is there enough power to satisfy the phone crowd? I would think apps would become more important after speed and responsiveness become adequate. I think this could be achieved with 32 bit at some savings.