Steam's working on that. Although you could just walk into a store and buy an ok-ish pre-assembled PC since 1998.
This. I know Windows is a hassle to get working right, but Steam works out of the box on Debian (and probably other major modern Linux distributions, too) on supported hardware. There are vendors that sell computers with Debian pre-installed too, if you'd care to take the time to look for one, and they'll select good hardware for you. You could even ask one of those "enthusiasts" who knows their shit if the computer you're about to buy is actually any good before you spend the money.
Then, guess what? You just bought a console that can both run any game on Steam for Linux, and function as a general-purpose computer. Simple.
This is inaccurate.
To get steam working on windows out of the box was simplistic. (download steam.exe, double click steam.exe, follow onscreen instructions)
By contrast, out of the box Wheezy, required me to add in the non-free firmware for my card (which required altering the sources.list) and installing that and rebooting, then writing an xorg.config file THEN I had to do the following steps.
http://steamcommunity.com/app/221410/discussions/0/864958088310067952/Which didn't work because I had to remove two packages from that ling list. (no idea what the / is supposed to do either)
Then I had to force the install of libcurl.
THEN and ONLY THEN did it work.
Out of the box Debian may work for the current testing version with a newer video card, but not wheezy with a Radeon HD 4890.