Not that it’s even one of my favorites, but I was a little surprised to find Rosemary’s Baby absent from this list. As for my personal favorites, surprise surprise, they’re old. 🙂 The Black Cat (1934) is one of those that only really introduces its cult in the third act. It’s a brutal, twisted, but at the same time charming classic, with by far the best Karloff/Lugosi pairing ever. The Seventh Victim (1943) doesn’t make its Satanic cult anything too outlandish or extreme; their philosophy is fairly easy to grasp, their actions and motivations believable, and their threat is in a way most disturbing for its very mundanity.
As far as Rosemary’s Baby goes, you know I’m more of a 21st Century aficionado. I did, however, give it a mention and a bit of historical context under House of the Devil. I think the acting and writing is great, and the ending is brilliant, but it does feel dated.
The 21st century movies you are slave to will not stand the test of time to the extent that Rosemary’s Baby has; it may seem dated in some ways, yes, but I think you are viewing a 1970’s movie through 21st Century eyes, a bit like someone watching the 1933 version of King Kong mocking the special effects employed! Rosemary’s Baby is a cult horror masterpiece! Why? Because it broke new ground; the first of its kind, because it adopts the psychological approach over the blood and guts one!