I'm going to say "Not in any meaningful sense". Some elements of any given game are tied more or less strongly to the genre, the setting or the fiction.
Every time you choose a game (to buy or to run) you can benefit from considering how much of the published material you want to keep, what you want to change and how much you want to swap out.
The more a game has in it, of course, the more you can run it without using all of it.

For example take vampire
You want to run Vampire in a high fantasy setting? Sure. Keep the rules but tweak the fiction. Change the clans if you want to. (I've played it and it was fun, though I died too quick because my character wasn't willing to keep her head down while working out this vampire thing.)
Or you want to run a vampire game but don't want the clan politics - remove the clans and Vamp on
Or you want Vamps to all be the same, so you say "all clans have access to the same power list" or "All clan powers are gone" and off you go with clans all equal as far as the rules go
Or Vampire run using D20. Keep the fiction, make the clans into classes (ooo, would you allow multiclassing?) and off you go.

It's all "bits of the game that you can use or not"