I might be an old soul, but It just isn't Halloween until I've watched some of the classic 30s-40s Universal Monster movies.
My favorites are the Frankenstein movies. The original film, my personal favorite Bride of Frankenstein, Son of Frankenstein, Ghost of Frankenstein, and Frankenstein Meets The Wolf Man (the first crossover in cinema history, right?) all range from, at worst, entertaining, to at best, awesome classics and some of my favorite movies ever. The weakest one is House of Frankenstein, which is really a Frankenstein movie in name only and just an excuse to cram all the monsters together without much care or thought.
Dare I say the Universal Frankenstein movies make up my favorite horror movie series? I mean, they aren't scary by today's standards, but there is a sense of wonder to them that just can't be beat, and I can watch them a million times and not get bored with them. And there are so many performances I appreciate like Boris Karloff as The Monster (he absolutely breaks my heart in Bride every time I watch it), Colin Clive as Dr. Frankenstein, Ernest Thesiger as the deliciously evil Dr. Pretorious (one of the greatest movie villains ever, fight me), Basil Rathbone as the cursed Son of Dr. Frankenstein, Elsa Lancaster as The Bride (only on screen for a few minutes, but definitely leaves an impression), Lionel Atwill as the Inspector, and Bela Lugosi as Ygor. All memorable in their own ways.