I love horror but apparently I don't vibe with a lot of recommendations I find online.
I'd seen so much hype about Event Horizon and I absolutely hated it and didn't find it scary. I just watched Late Night With the Devil and whole it was definitely enjoyable, it wasn't the least but frightening. I also just watched Let the Right One In and really didn't like it. It also was not a horror movie in my opinion.
I will say one of my favorites is Sinister or the first Conjuring. Sinister for the stomach twisting dread and suspence throughout and Conjuring for the same.
I absolutely love horror movies and have a long list of fantastic ones but not very many of them actually scared me. Most of them have been named already but two I didn't see were The Babadook (2014) and surprisingly a Netflix movie called His House (2020) was actually awesome. One of my favorites in the last few years.
Yeah I actually think that my favorite horror movies are the ones that get me asking questions, rather than being scared. I like being intrigued by the evil, like in Smile (until the twist at the end, it was a perfectly good psychological horror that did not need a monster)