What about before PS2 (and I would include PS3 too), when advanced 3D visuals like atmospheric effects and dynamic lighting (remember that Splinter Cell was released in 2002, just about 5 years before PS3 made dynamic lighting possible for console games) would have been impossible on consoles? Even now, I see distinctions between my PS4's rendering of Metro: Last Light and that of my PC (even when the graphics card is a dilapidated 680GTX).
True, the quality gap has reduced considerably enough to discard the reliance on PC's to get the best experience. Furthermore, the console has enough horsepower to host all the AI and still run the most demanding network protocols without much difficulty. However, this is a whole different topic.
Even before the demise of PC gaming, Linux has been suffering from gaining popularity amongst gamers. SteamOS is a good step in the right direction, but it will take time as did the Steam market itself (I remember the old days of Steam with Half Life 2, having to get the connections sorted). I think the saviour for PC gaming will be Nvidia with their cloud-based rendering technology. In fact, Linux should be at the core of it, if Satya Nadella doesn't pull off another MSDOS and fool them into submitting exclusivity.
On the mobile front, Linux is already being avenged by the mighty Android.