These threads are really getting me to wonder at everyone's definition of a horror movie.
You find that with any genre. Blazing Saddles is a comedy, but is it also a Western? or a Musical? Film-Noir has a very rigid definition, and I know Martin likes to stay within those perimeters. However there are noir precursors, modern noir, non-American noir, and additional films between 1940-1964 that have noir elements. It dilutes the brand to where under the broadest definition, pretty much any crime drama can be called Noir.
I never thought of Shutter Island as Horror, even though Scorsese uses to spooky horror imagery for atmosphere and the central mystery is certainly horrific. The film's lighting and costumes also use Noir characteristics, but does that make it Noir?
I had a discussion with the person who created the list, which was made by compiling over 1200 other Horror lists. I found it strange that Eyes Wide Shut came up more often than Monsters Inc. "because it's 'psychological' and because of the dark atmosphere. Monster's Inc, on the other hand, has monsters but that's about it. It only appears on 2 lists and they are both 'monster movie' lists."
I replied, "I'm not going to make the argument that Monsters Inc. belongs on a Horror list, but there are scary moments (Spider-legged Waternoose on the attack borrows from a scene in The Terminator), a couple of intense scenes (like the Scream Extractor machine) and the creepy chameleon ability of Randall Boggs. Those are more directly related to Horror than a dark atmosphere.
What about Pink Floyd: The Wall? Certainly that has psychological horror, a dark atmosphere and nightmarish imagery. I find it strange that it's excluded but Eyes Wide Shut is not. I don't question how the list is compiled, but the reasoning of some of the lists themselves for including a film like Eyes Wide Shut but excluding Monsters Inc. or Pink Floyd: The Wall."