Purist For System
Check out GURPS, FUDGE, DC Superheroes, and EABA. You'll see what I mean.
Sometimes a game like this does focus on a given genre or topic, like the third one in my short list, but a lot of them don't and present their central mathematical formula or point-structure to be dressed up in whatever setting you want. It always seems to feel or be the same game in any setting, though.
A category of design which applies a distinct mathematical concept or set of relationships throughout all the simulated physical and other in-game causes; it is often used as a chassis for a wide variety of possible settings, characters, and situations. Such design often facilitates Simulationist play, at least historically. See Simulationism: the Right to Dream.