Yes, yes it is
As a seven-year-old in 1980, I had a front row seat (literally, as a sneaker-in of theaters) to the explosive evolution of horror films in that time. I've been vocal online for years about how a deep pedigree in horror is great brain food for the aspiring game master. As spooky season reaches its veil-thinning crescendo tonight, I'd like to take that position even further.
Premise: The presence of monsters is intended to frighten
Premise: The supernatural is intrinsically frightening
Premise: Fantasy role play employs a litany of other horror story devices
Thesis 1: Fantasy role play is always a form of horror
Thesis 2: Masterful connoisseurs of horror will make better GMs
Before you leap forward to inform me how many sessions you have played without any combat, suspense, monsters, dark themes or dimly lit environments, let's jump up a level of abstraction. Without some looming doom or 'it's out there' suspense, no game of any kind can endure. Role play without conflict is like a board game with no winner, or painting with your eyes closed: you might be doing something, but it will be earn some quizzical looks. "Is he making art?" "Not sure."
Granted, there are many genres out there that employ suspense, foes, struggle, heroism, and the like that are decidedly NOT horror. The difference that separates these genres is monsters. Action films, mysteries, and the like do not inherently include monsters. No matter what brand of fantasy role play you enjoy (vernacular "D&D" here) there has GOT to be a monster or two. Monsters as are central to D&D as bread is to sandwiches. Monsters serve one key purpose in all stories that include them: to make us gasp with fright.
What is it about monsters that scares us so? Is it the dripping goo, the sharp teeth, the weird fingers, glitchy walking style, glowing red eyes? Those things certainly do add to the tone, but the deeper truth is well-known by horror writers old and new: monsters scare us because they hint at the unknown. Another nickname for the height of the unknown/unknowable is the supernatural. This word defines itself in what we do not and cannot know. Monsters arise from the unknown. They are beyond animals or humankind... they come from some other origin. Even if they just want to be friends, they scare us because they break our sense of what is real. The unknown, and all its spawn, are frightening.
Clearly not ever D&D table has supernatural elements. It is plausible that a table might have no magic, no weird creatures. Bone-dry medieval simulationism is a variant we can imagine. I would argue that even this form of game has a monster lurking somewhere. Even history itself, the things that actually occurred, base their stories now again on monsters. So even a perfectly realistic tone would have to acknowledge that unknown forces of wrong-doing are conflated as monsters. Besides, without at least one boogie man to root out, who really wants to play?
As for the litany of other devices, take a moment to conjure up memories of your recent or favorite D&D sessions. I see laughing friends, fickle dice, bodies floating in water, an inky mass of writhing tentacles, blades in the rain, blood soaking into stone, hooded acolytes, grumbling music, wide eyes, breath held during a die roll, and smiling relief in the wake of terror's grasp.
Horror or fantasy? Hard to say, comes up on both searches
Our games, week-in, week-out feature all kinds of devices from horror storytelling! "What's behind this door?" "It's really dark down here." "What in the world is that THING?" "Oh, that was grewsome!" "No, they've eaten Carl!" Adventurers aren't called so because they reside safely in office jobs and reasonable walks home. They are called so because they dare the terrible, delve the dark, dare the dangerous! D&D sessions love a spooky backing soundtrack, dim light, black robes, candles and monstrous voices! We revel in the leaping-out, the shocking kill, the impenetrable shadow, and the hideous reveal. Adventurers gather clues, meet frightened villagers, and fight to muster their own courage in the deep! D&D is horror!
Ok, Hankerin, calm down. Maybe you're right, but... so what? Well, my second thesis is the fun one! If it holds true, and you care (as an aspiring GM) you are given an edict to research horror year-round. Don't watch it all, be discerning! Partake of the very best, for it is terribly bountiful. Leave your old classics and comfort zones... dare new frontiers! Horror is better than ever these days, but it takes a good eye to truly know the genre. Sure, Samhain is when everyone is into horror, but you're reading these words. You are a game master of distinction. You are a seeker of the highest levels at the table. If this sounds like you, Halloween is all year round, and it's time to dim the lights.
Good Samhain, everyone, may your fires be bright!