It should probably come as no surprise due to my username, but my favorite genre of film is horror. I've been watching horror movies since I was 3, the first one I ever saw being the original Child's Play from 1988. I've never been scared of horror movies and just really enjoy all the stuff you can do in those sorts of movies. I miss the days of practical effects and I also miss the sort of music you'd hear in horror movies from, say, the 70s and 80s, especially the songs with synthesizers. I sometimes daydream of trying to work my way into the movie industry to make a good old fashioned 80s sort of horror movie.
I'm more fond of horror movies from past decades, specifically from the 80s and all the way back through to the start of cinema. I will watch modern horror films, but I kind of need to hear good things about them before I'll bother to check them out because there's a whole lot of garbage out there nowadays and I have other things to do than dig through the muck to find the gems.
I tend to like to watch horror movies all through the month of October for a big 31-day horror movie marathon. I've seen a lot of the worthwhile ones by now, but I still sometimes come across things I hadn't heard about.
psychological thrillers are the best!! i forget the name, but this one came out fairly recently about a guy with multiple personalities that abducts some girls. really scary and interesting.
Documentaries, preferably from the 60s-70s when they weren't overly polished and more raw/authentic and not edited so it almost becomes a reality soap or stuff.
Superhero movies are basically half of my life. Some comedy is good as well though. And pretty much any movie series that started in the 1980's with the addition of Star Wars, as it started in 1977.