You really don't think film critics being different from the general population has anything do with it? They're trained to see things in movies that most people don't. I get that you want people to say "selection bias" but that's not even close to the only significant factor at play here. You have two populations, which is also a classic statistical phenomenon. You even get close to this in your discussion of selection bias—they watch a lot more movies, and are thus more experienced—but you don't seem to want to allow this, which seems odd.