i believe i have pinpointed what i have thought about horror movies to an articulated response!
I think that there are two qualities (more, but these are the two main ones i want to address) that horror movies are separated on, and that i think only one should qualify a movie as horror.
i think a good quality of horror movie is more about fright. how scary something is.
what i dont think is as much quality horror is upsetting.
now, i think scary movies can often be upsetting, and so too can good horror movies, but i think that a lot of "horror" movies running around are not scary, just upsetting.
for scary, an example is the movie The Haunting from 1963. the castle is scary visually, the sounds are scary, there is an eerie feeling that is frightening. no gore, nothing.
the saw movies are upsetting (and i think the first one is a well done movie, and the second is cheap messy fun) and not scary. there is fear, but its usually more of "that would hurt" or something visceral. not "that scares me" like the Haunting, but more a sucking air between your teeth and wincing, much like watching vids of people racking themselves on skateboards.
the Exorcist i would say is scary and upsetting (not to me, i think it has a happy ending).
i think the movie The Ring is mostly upsetting with a little scary, but not much (i didnt think so, but some people do, meh).
jeff goldbloom's "The Fly" is very upsetting, but its a type of horror known as body horror.
a movie i think is very upsetting but also very scary is The Thing, the john carpenter film. the dog scene in particular is upsetting because, well, innocent lovable dogs are being hurt in horrible ways, mutilated, and that lingering feeling of when are they dead or part of the Thing or etc drives (at least me) nuts. but the lighting and music and sounds of the Thing are frightening in a monster under the bed or eyes peeking in the window kinda way. scary.
i think Gremlins is very scary, but not too upsetting (except that scene at the end with the melted gremlin corpse... thing).
"paranormal activity" is, i think, more scary than upsetting.
Se7en is more upsetting than scary (way more).
i just think that a movie thats scary without being upsetting (or balances out the scares with upsets) is a better horror movie. not saying gore is bad (zombie movies, for example) but that scares are better.
i like the old greek notions of catharsis, in that tragedies were meant to be stage performances and you were to remain slightly but always removed from the situation so that you could walk away from it and not be bothered by the end. sort of "well damn, glad that doesnt happen to me, better make sure i dont screw up like that" and then walk away and go eat and laugh. or think but on an intellectual level, not a fretful disturbed level.
movies are a much more powerful medium, however. so this is harder to maintain, and i think it is why i love older films over newer ones. yes, avengers is great, but the original superman with reeves is something else. yes, nolan's dark knight is awesome, but tim burton's batman is important. yes, paranormal activity is scary, but Exorcist is a trip.
not to mention the one rule: CGI is not scary. as in, it is not as scary as an animatronic or actual set piece, or something somewhat physical in nature. i dont even feel its as grand in a general sense.
screw phantom menace, i want return of the jedi.
screw when darkness falls. i want Nightmare on Elm Street.
the only exception with CGI is when its too subtle to notice. but this is outmatched by animatronics that can be in direct lighting and bid adieu to subtlety and still rock socks off my goose pimpled feet.