Well, those of us that were already coding for Windows back then, remember that what brought game studios to Windows was WinG, the percursor of DirectX. http://en.wikipedia.org/wiki/WinG Gabe Newell had nothing to do with it.
In DOS mode you could easily get full-screen, high-frame rate game graphics. In Windows you'd be lucky if you could push more than one frame per second, the Windows GDI was absolutely brutal.
Linux is a lot further ahead, so SteamOS has a relative head start. If Windows can be made into a first-class gaming platform, so can Linux.