The Man Who Laughs is a blend of many genres, but it definitely feels like a horror movie. Unlike many horror films, however, this is one where the "monster" is also the hero and you root for his survival.
The Golem: How He Came Into The World is actually the third part of a trilogy about the eponymous creature, but it's the one that's the most widely celebrated today. Like a couple of other films on this list, it's one of the great German Expressionist films.
Lon Chaney made it his business to look as horrifying as possible in most of his films, but I don't know that any of his creations topped his truly frightening Phantom.
I've never seen The Cabinet of Dr. Caligari in its entirety but the bits and pieces I have seen were... unsettling, to say the least. For now, though, I'll just have to take the word of many other listmakers that it's one of the best horror films (or films, period) of all time.
No romanticized vampires here - just sinister-looking Max Schreck in his definitive role. It's one of the greatest films ever made, a spellbinding viewing experience that you can watch over and over again.