I don;t rally have a favourite most are pretty laughable. The Ring was quite good just for the cool way the "monster" walked. Nosfaratu was pretty epic as well especially since its so old. And of course Shaun of the Dead really scary.
I really love the old 'Gothic' horror films of the 1950s to 1970s. They really started in 1956/7 with 'The Curse of Frankenstein' with Peter Cushing, 'Dracula' with Cushing and Christopher Lee and 'The Mummy' with Lee. There were 6 Frankenstein sequels and no fewer than 8 Dracula sequels. My particular favourites Tomb of Ligeia, with Vincent Price and The Fall of the House of Usher, both based on Edgar Allan Poe stories.