Well . . . I suppose you could say that the "horror" in Pet Semetary is internal. That is to say, the characters create the horror by making use of the cemetery, even though they know they shouldn't. The darkness at the end of Revival might seem more base, simply because the implication is that it is inevitable. It's outside us and it's waiting for us and there's nothing we can do about it (although I seem to recall some speculation that the vision could somehow have been some kind of psychic "mirage" and not necessarily "fate" -- I'll have to go back and look at it).
Louis Creed keeps getting something he doesn't want from the monkey's paw, but at the end of that story, he still hasn't lost his faith that somehow he can "get it right next time." To me, that's a much more fundamental horror. If I were to discover, incontrovertibly, that the Jesus people were right and I'm going to burn for my sins, that would bother me exactly to the extent of . . . say . . . losing at a game I hadn't yet learned how to play. But making the same mistake over and over and over again, and cheerfully telling yourself that it will all work out okay in the end (something I know a little bit about) . . . well . . . that is orders of magnitude worse.