That must be how Universal Studios think of it. It's great as a video game, yes, but adapting it into a movie as great won't be as easy as telling Jack to do shit just by saying "would you kindly", as most game adaptations we know.

But let's say Verbinski successfully make a BioShock movie that don't fail, I agree with you--non gamers would drop their jaws I'm sure of it.
I do feel kinda nervous(?)... and doubt too about this, but there's still a small part of me that want a BioShock movie to happen.