Switched from Windows to Ubuntu 2.5 years ago, 2 years ago, I tried Arch and stayed with it until now. I tried various desktop environments and window managers, but I always came back to Gnome. It's the most polished and I really like the workflow of it.
Concerning why: Well, Windows is just bad at so many simple things compared to Linux. Yeah, Linux has its problems, but I can see the progress of them being fixed, whilst on Windows you can still find the same issues you could find 15 years ago. Like, WTF. Another major point is privacy. It's no secret that Microsoft is spying on its users. Linux is open source and thus as transparent as it gets.
I also play games on Linux. Occasionally, it needs some tinkering, but about 95% of my Steam library works (most of the time, even with better performance). I also do programming. There's no doubt that Linux is just the superior OS for developers, unless you have very specific needs.
Nowadays, I have no machine left running Windows. And for the moment, I'm not thinking of switching to anything else.
X probably stands for the idea of his “everything app”.