Oh that's interesting. For me, zombie films are definitely horror but in the same category is anything uncanny from Lovecraft novels, classic Christmas ghost stories, Hammer Horrors to the crudest of slasher films.
The most horrifying things for me are psychological stories like the two I've just linked to because they're almost real
La Cabina is rooted in Spanish history. It's a horror fantasy about the Franco era and the persecuted and bystanders - made at the time it was happening, which was pretty brave.
I'd say zombie films are definitely horror in the same way because they almost be real like Dawn of the Dead, which uses horror to talk about consumerism and politics.
Or films such as They Live! or Invasion of the Body Snatchers.
I'd put comedies such as Shaun of The Dead, The Lost Boys, Scream, both Fright Nights, Drag Me To Hell and The Evil Dead in the same category.
So what is and what isn't?