The geek imagination rarely extends beyond fan fiction.
This is true of all people. Even original characters are simply embodiments of pre-existing archetypes. A truly new character or story would be incomprehensible, since you couldn't relate to it.
That said, while Sturgeon's Law is in effect for fan fiction as well, so is it's reverse: good fan fiction is good literature, and has an added advantage of being able to draw from pre-existing mythos, often with considerable re-interpretation. And of course Cthulhu mythos shows its tentacled head everywhere.
You know, arguments based on pretending a huge group of people are really a single person rarely make sense.
The geek tends to forget that patents and copyrights are meant to be an incentive to create something of your own, something new and something better. It's telling, I think, that the only two video game themed movies that are arguably worth a damn, Tron and Wreak-It-Ralph, both came from Disney.
What should it tell us, exactly speaking? That once you've filmed - or re-filmed - all the stories other people came up with, you can afford to try something else? Especially since Disney can always keep on milking Mickey Mouse, which is the whole reason eternal copyright exists in the first place.
Or do you simply work for them?