Strikes me that we're not quite coming in from the right angle.
I'd see "optimised for PC" as making use of the available resources.
In the case of most players, you're probably looking at a taking advantage of at least 4 cores, graphics settings to suit a wide variety of graphics cards and the ability to make use of RAM when it's available, so as to reduce load times.
I'm unaware of anything that I currently play that does the above. I got the impression that Doom and Wolf are probably the best proponents. Does the Unreal engine do the above?