A true classic, this is the story of the Man who would play God. The novel, originally subtitled "The Modern Prometheus," understood that, and the movie follows the theme.
Viktor Frankenstein is not the monster, but the man who is himself a monster. He creates his creature, gives it life, and when he finds it repugnant, abandons it to the cruelty of the revenge-bent villagers.
The black-and-white makes the movie, if anything, more creepy. There's something eerie about b/w movies.
I'd rank this in my top 100. As horror movies go, I find it far more watchable than Dracula or The Mummy.