Yeah, that occurred to me after I asked the question. Still waiting for at least two from the '50s that have eluded me forever to show up on YouTube -- I've Lived Before & The Whip Hand.

One of these years ...

I never saw either Rosemary's Baby or The Exorcist until a few years ago, and enjoyed them thoroughly, in spite of feeling like I already knew them both through MAD magazine parodies and the like. These are expertly-crafted films, so they're worth watching on that score alone, but the tension and fear still worked at a visceral level too, so it  wasn't just a cold, academic exercise

And I too did read The Exorcist a a kid - I think sometime in the mid-70s, probably a few years after it was on the best-seller list. I know it was at least a couple years after the movie was out. Certainly one of the scariest reading experiences I can recall. 

I'm old enough to remember the incredible media furor over the movie of The Exorcist - there were discussion programs that would devote practically an entire episode to talking about it and some of the stories (urban myths?) of the reactions of audiences and some individuals were almost as scary as the movie itself seemed to be to 11 or 12 year old me. It made the Devil seem like a real-world terror.

I still think that for anyone who - like most of us here, probably - was brought up in the West (however you care to define that), even if you don't count yourself as a believer, supernatural horror stories based on Judaeo-Christian mythology will almost always strike a deeper chord than anything else, just because we absorbed it as kids from before we were old enough to think. And for people of my age or older (not so sure about those younger than myself), all that was taken much more seriously back then, even if your family weren't particular religious, as mine weren't. It was just an accepted part of the background, it was just there. So I'd say that for many, if not most, people from the West who grew up in that era, for a certain time in their childhood, even if it was only until they were old enough to examine it make up their own mind, God and Jesus and the Devil were about as real as the Prime Minister or New York City or anything else you accepted as existing without ever having seen it. So stuff like the Exorcist or even The Omen had a certain resonance that I think is hard to match without playing on those same deeply embedded concepts. 

Just finished watching Curse of Frankenstein for the second time tonight, and I still don't get it. The story is decently engaging, and that one shot revealing Christopher Lee was phenomenal, but beyond that, Christopher Lee doesn't do anything all that impressive as the monster, and the interpretation of the story is noteworthy only in the back story it provides for Frankenstein, explaining why he's so cold and detached to people. Much as I love Peter Cushing, he's no Colin Clive, and as groundbreaking as the use of technicolor blood might have been to 1957, I still find it less scary than the moody atmosphere and loud buzzing machines of James Whale's films.

As an avid fan of the Hammer Dracula films, I just don't understand what's so great about this one, and people continuously say it's the best of the Hammer Frankenstein films, so I'm wary of pressing on with the franchise.

I can agree with all of that.

Except that the Hammer Dracula sequels were poor. While I agree nothing lived up to the first two in terms of writing and complexity, I find them ALL to be great fun except for Satanic Rites, which I consider pretty much unwatchable.

So what about the Frankenstein sequels? Worthwhile?

I've never been a big fan of Hammer, though I really think I'm just not a fan of the big two series, Frankenstein and Dracula (though Cushing is always good. I don't agree with the Hammer take on Dr. Frankenstein).

I also re-watched Black Sabbath the other night while scooping out pumpkins. It's an amazingly well-made film, and probably Karloff's last great performance (excepting Targets and the Grinch).

The final story in the film positively floored me, but I couldn't get into the first two.