The Windows/Apple/Linux/Android war. Here's a cat's 2 cents, this is coming from a computer technician.
Windows:
They go through their up's and down's. Like mentioned earlier, xp was great, vista sucked, windows 7 was the best operating system and windows 8 was a new idea that both failed and succeeded at the same time.
Windows is ideal for gaming, thanks to its customizable PC parts. While a Mac is great for graphical design.
Windows has the upper hand for office buildings, whether small or big, since all computers can be linked up to one domain (its so useful).
The downside to Windows is that every other operating system turns out bad and we end up waiting an extra 6 months or so for a newer/better operating system.
The Windows Phone is great. While lacking in apps, the current available apps are good enough to make a phone run and is mostly made by Nokia (RIP), can't beat that. The connection between the phone and the computer is much nicer than iTunes.
Apple:
Its an operating system designed not for people who have little to no computer knowledge. It can get some time to get used to, but overall, its a nice clean looking operating system. Apple like to stay the same, in layout wise. Unlike Microsoft, who decided to just change the layout, they kept the same layout pretty much the same for years. Which can be a problem with some (I'll explain later)
Apple products are completely overpriced. You pay so much just for the name "Apple". Windows and other operating systems are able to provide much more for a lower cost.
For gaming, even if you spend $1000 - $2000 on an iMac/iComputer, which might have the same specs as a PC, the PC will still be stronger.
Apps for the iPhone is much bigger than the Windows store, but there are a lot of apps you have to pay for. So its both a pro and con.
Linux:
I don't know why, but Linux always gets so much hate. These light weighted operating systems are perfect for servers, small office work and if you want to get into programming. Best of all, they are free. Without Linux, we wouldn't have Windows or IOS.
The programs are executed like the Apple store for iMac. You go to a store and download it (buy it if there is a price). Linux gets just as much support as Windows does, and if there are programs just for Windows, you most likely can run it on Linux thanks to Wine.
Android:
One of the main reasons I think this succeeded was because it is constantly getting updated, adding in NEW USEFUL features (unlike Apple) and you just overall have more access to the phones folders (like a pc, how you can go in downloads, pictures etc), but it comes to a price. It is also very unstable, which is why some people prefer to go to Apple or Windows. I've used several Android phones and found that they start to freeze and crash after a few months, unlike Windows or Apple.
The app store makes up for this, there are so many apps for it and they are mostly free, unlike Android, which could be another reason why people prefer it.
So overall (used this word a lot), each operating system have their pros and cons, personally I like to use Windows (currently have 8.1), I have a Windows Phone (Nokia Lumia 920) and an iPad for reading and some games, oh and my work phone is a LG Android, I forget the model and Android version.
Windows: Office work and games (Stable operating system, perfect for just about everything)
Apple: Graphical design (can get viruses, unlike what apple users claim)
Linux: Servers (Due to it not using so much computer resources, its great for servers)
Android: Apps apps apps (apps apps apps)