Oh really? That's cute. Tell me how many games on Steam work on Mac. Oh don't worry, I'll wait.
That's a yes and no answer. Can you do it? Yes. Is it legal? Technically no. If Apple wanted to, they could legally sue everyone making Hackintosh computers, but they won't so long as you don't sell them. Can you do it? Yes, however you need to have VERY specific hardware, for example AMD CPU's aren't supported, and I don't think their GPU's are either. I'm pretty sure only Gigabyte motherboards work, too. And have fun finding the drivers to make them work.
You do realize, before they stopped making them, the $1700 Macbook Pro had the same parts as a $700 Windows laptop, right? Matter of fact the Windows laptops, a lot of the times, had a bigger hard drive, more RAM (they seriously kept selling a laptop with 4GB of RAM, at that price?!), and, if you looked hard enough, a better GPU. The MSI GS60 Ghost Pro 3K edition has a screen with a higher resolution than the Retina (BOTH of them), an m2 SATA SSD (not as good as the PCI one in the Retina), a HDD, more ports than the Retina, and costs about $700 less. When you buy a Macbook you're paying for the name and the ridiculously expensive method they use to build the enclosure out of aluminium. Literally everything else is the same you'd find in any other laptop.