Full of 80s cheese but my favorite horror movie has always been Prince of Darkness (1987). The 80s cheese actually makes it better. Also a good example of a movie depicting a future that is now long in the past (1999).
I liked The Devil’s Rejects. I enjoyed the subversion of the 70s slasher film, and the antagonist-as-protagonist angle. It’s really more “torture porn” than character study; no one will ever confuse it with Henry: Portrait of a Serial Killer, but it’s still stupid fun.
Always enjoyed the Hellraiser films, if only for their insane imagery. Bloodline is probably my favorite of the series because there’s actually a compelling story there.
Other favorites are Midnight Meat Train, a very small film with a ridiculously famous cast (Bradley Cooper, Vinnie Jones, Leslie Bibb, Brooke Shields), The Host (Korean monster movie), The Void (Cthulu-inspired, and now that I think about it, it actually has a lot in common with Prince of Darkness), and, if it could be considered a horror movie, Trollhunter (2011, Norwegian). The last one was set for an American remake but got cancelled.
As Above, So Below got bad reviews but I enjoyed it. I really liked the unusual take on Hell.
I’m also a fan of the Jeepers Creepers movies. They’re summer teen slasher schlock, but there’s something about the Creeper and its mythology that are compelling to me. 2 is the best one, IMO.
Everyone has seen it I’m sure, but Dawn of the Dead (2004) is easily the best of the Romero remakes.
And then there’s my love of stupid, extremely low-budget old horror films like Basket Case.