Back in the early 20th Century, the undisputed kings of horror movies was Universal Studios. Yes, that Universal. They may not have invented horror movies, but they certainly pioneered the genre in a time when the cinematic media was in its infancy.
Think of the classic monsters, what comes to mind? If you said Dracula, Frankenstein, the Wolf-Man, the Mummy, Invisible Man, and that Creature from the Black Lagoon, it was Universal that brought us the definitive iterations. And the three actors that helped to define many of these movies were Bela Lugosi, Boris Karloff, and Lon Chaney, Jr. (whose father, Lon Chaney, brought both The Hunchback of Notre Dame and the Phantom of the Opera to life in a couple of silent films for Universal a decade prior), were Universal regulars.
The Golden Age of these movies at Universal were the 1930s through to the end of the 1940s, the end being signaled when the studios decided to get Abbot and Costello involved and turn these into comedies. If you wish to view these monsters in their prime, though, here’s a list to include in your Halloween viewing que:
Dracula (1931, with Bela Lugosi)
Frankenstein (the 1931 classic with Boris Karloff as the Monster)
The Mummy (1932, with Boris Karloff)
The Invisible Man (1933)
The WOlf Man (1941, Lon Chaney, Jr.)