The Omen is one of my favorites. It could very well be interpreted as an incident of mass hysteria around one family. I believe Rosemary's Baby was left open to be interpreted as a possibility of Rosemary experiencing a pre and postpartum depression episode. Both movies never make it clear and remain enigmatic.

That is almost never done now. Everything is given to us. No one ever has to interpret anything or come to a decision on their own. Even the news has slant, just in case we don't have the brain cells to properly condemn bad events.

I don't mind sequels, if they are created with a stand-alone ethic. I really hate sequels that just rehash everything that occurred in the last film. Most are like that, because the makers really just want easy money not a good product.