Incidentally, it's the same issue at stake for things like "Hell Houses" around Halloween: can people be "scared" into believing in Jesus? Should they be?
All of these— "Christian Horror" movies, Hell Houses, and so on— are based on the premise that the most effective way to motivate belief is to present the fruit of disbelief. Christians believe that those who do not have salvation through faith in Jesus Christ and His atoning work will suffer judgment and condemnation as punishment for their sin. The basic point of these approaches to "evangelism" is to present the reality of this as starkly and, yes, as frighteningly as possible.
What is the typical result? From reports I have heard from friends whose congregations hold such events is that many express their desire to avoid such a fate. What comes after this expression, though, is the key; it is certainly possible for someone to face the reality presented in a "Christian Horror" movie, believe that, make a response out of fear, and never know the hope of the whole Gospel.
A fellow pastor told me he once had a young man indicate his desire to join the church, and so he met with the man to explore this desire. He asked the young fellow, "why do you want to join the church?" The man answered, "because I don't want to go to hell." My friend then said, "and on what basis do you think you should be spared going to hell?" and the man responded, "because I heard a preacher tell us all about hell, and he said, 'if you don't want to suffer in hell, then walk forward and indicate your desire to unite with the church.' And I did!" The name of Jesus never crossed the man's lips, in spite of his sense that he should join the church and avoid the perils of eternal condemnation.
This is my point about Hell Houses and hell-oriented movies, as well. While they teach plenty about hell and probably a good bit about Satan (probably even a fair amount about the viewer, and his sinful condition), do they offer anything of Christ? The Gospel must be much more than simply telling me about my sin; it must primarily be about Christ and His work, in addition to my need for Him.
Finally, I also have substantial questions about using fear as the primary means by which we urge people to God. The clear teaching of Scripture is that God does not seek merely to scare us, but to be reconciled to us. If the central idea of our evangelistic outreach efforts is how afraid we should be, how do we then teach those new professing believers that their primary orientation to God is not one of terror but of adoption?
"For you did not receive a spirit that makes you a slave again to fear, but you received the Spirit of sonship. And by him we cry, 'Abba, Father.'" (Romans 8:15)