People will want to game in settings like Harry Potter, Star Trek, Doctor Who, and others. Not everyone will want to have their game be about punching strange things, and there will be a desire for a mystery akin to Call of Cthulhu (with less death, of course).It is important also to note that Star Trek is a completely unplayable game world and is in fact a classic example of what not to do when designing a cooperative storytelling game. Imagine: you're on a ship and weird green things are appearing in the hallways and causing energy conduits to explode. Oh noes! What do you do?
Seriously, what the heck do you do? It's Star Trek, what the characters do is wander around running diagnostics until theyfigure out what radiation emissions from the crystal aliens are making their shit explode and then they throw some super physics at the problem to either shut out the harmful rays, solve the deeper environmental problem causing those rays to happen in the first place, or just frickin leave and hope the problem doesn't follow. But what the heck does a player do? The characters are just making extended science tests until they win the adventure, the player has seemingly no input whatsoever.
There's no game there, it's just a narrative. The viewer has literally no basis on which to anticipate what the next group of forehead aliens are or do, and has no idea how to solve any particular problem. Everything that happens is the equivalent of Game Master Exposition.
Rather than just shake your head and deny, what kind of mechanics could one use to overcome the difficulties in such a goal?
My own personal ideas include a combination of the GUMSHOE system with FATE points or checks to 'create' facts within a comparatively narrow field when used.