My components for good horror:
(the top three of which have already been listed by Nicky, deron, and Rainey )

Also, I'm limiting this to the cinematic.

1. The unseen.  Stephen King writes about this in Danse Macabre (and then proceeds to not do it in everyone of his books thereafter).  Don't show me the monster behind the door.  I don't want to know that it's 40 feet high and dripping saliva, because anything you can show me is not nearly as bad as what I can imagine it to be.

2. Suspense.

3.  Plausibility.  If you give me a plausible context and believable characters and dialogue, I'm there.  I will willingly suspend that disbelief all the way.  The Blair Witch Project had me terrified for days and it had mostly to do with the fact that I know idiots like those three kids who would do stupid things like not mark their trail before going blindly into the woods.

4. Strong characters.  It can be the villains.  It can be the heroine.  It can be that adorable small child.  If I can't identify with someone (and I frequently can't), then give me someone who will engross me.

5. Atmosphere.  The best horror films/tv shows do this well.  It's hard to explain what I mean, but I think you all do.  

6. Adequate production values/historical accuracy.  I'm one of those shallow people who will find themselves completely distracted by the fact that all of the women in a Hammer film set in the 1800s have 1960s hair or find myself laughing hysterically at someone being menaced by a vicious plastic vine.  Know your limitations and go from there.  If the Blair Witch crew can take twine, some rocks, and some sticks and scare the bejesus out of me, then it can be done.  If you can't do it, then don't try.  

Tall order, I know.  

This is a great post, btw.  I really don't want to get into the Christianity aspect of it, but it may be of interest to note that most faiths hold that if you're going to accept that there is good, then you have to accept that there is evil which leads into the "if there's a God, then there's a Devil" theory.

Luciaphil

I don’t have children but if I did I would have no problem letting them watch “Dark Shadows” at any age (I let my dog watch - he's into the wolves  ).  Growing up I remember that my own mother never had a problem with my sister and I watching this show or really anything else for that matter.  The violence and sexually explicit issue never entered into what we watched back then because, for one thing, I don’t think things had gotten explicit enough for her to even notice yet (really showing my age eek!).  By the time she notice did we were old enough to make our own decisions.  

Now that I’ve seen every ep of DS – and some more than once – I can honestly say I find absolutely nothing offensive about this show.  I can vaguely remember the movement to stop the show back when. I also remember wondering what their problem was and doubting any of them had ever watched the show in their lives.  After all there are tons of things each and every one of us find offensive on various levels yet most of us simply opt to turn off whatever it is that is broadcasting it rather than attempt to annihilate it.  Several years ago I griped about a popular local radio program for being so crude.  Then one day they finally hit the last straw with me when they started making jokes about people starving in Ethiopia.  It was on that day that I realized I had control of the situation and I turned my radio off never to tune them in again.  These idiots of course continued to prosper and are now nationally syndicated – but to me they are non-entities.  Why the self-appointed pious wanted to whine about Dark Shadows of all things I don’t know.  As my grandfather used to say, they need to keep their own noses clean and let other people worry about theirs.  

I will say this too - as a follower of the Christian faith I do not find this show offensive or “dangerous” on a spiritual level either.  I am drawn to this show for many reasons that I’ve mentioned before – the big, mysterious sprawling mansion, the romance, and fascinating struggle between good and evil.  I do not consider any of those things bad or wrong any more than I feel guilty for reading Anne Rice, Stephen King or Dean Koontz.  I also don’t now or did I ever feel a burning desire to become a witch, vampire or even a corrupt member of the clergy (LOL).  Of course, it helps to be able to tell the difference between fact and fiction – which I think most kids are able to start doing about the time they learn to talk.  

LOL!  Yes, that is probably the reason.  Still, I think this was psychologically far scarier than anything else behind those other doors.  Seeing our own tombstones complete with a death dates reminds us of the one inevitable thing that most of us fear the most.  

When I see those doors I still think Monty Hall could have done a great parody of the Dream Curse:

"Now Miss Stoddard, for the grand prize, will you take what's behind door number one ... or door number three ...  or will you keep the money?  

LOL!!  Yes Jennifer, that's the one! The girl wound up marrying him anyway, and look what it did to her.  Yes, he did look alot younger,  but still had his "fighting" wits about him. As soon as I heard all the yelling, I knew it was him,  didn't even have to look at the TV.  

Did anyone happen to catch Roger Davis (Jeff Clark) tonight on The Twilight Zone? I happened to be in the next room when I heard all this yelling & screaming, and sure enough, there he was,  still "fighting to the end!" Some things never change.