Omen 2 is less than the sum of its parts. To be fair, its cast, music and production values are all rich with quality. Lance Henricksen is always good value and Leo McKern is class on a stick. The deaths are good and nasty and it's a bit shocking to hear The Music and see The Crow... but at the end of the day it's not scary. Basically it's the happy everyday tale of a demonic teenage serial killer and his adoptive family, sorta like The Waltons with supernatural murders. As horror it feels as if it's going through the motions.
I blame the story. Terry Pratchett says he got the idea for Good Omens by watching this movie and thinking "wouldn't it be more interesting if Damien tried to rebel against his destiny?" but in a way he almost does. He's definitely the film's most interesting character, and oddly the most sympathetic too. Everyone else is either an Evil Satanist Minion or a victim-in-waiting. You know the good guys won't win, if only because this wasn't the last film in the series.
But this doesn't help the horror. Damien's struggle with his identity is quite interesting to watch, but it means he's not scary. The script for Omen 2 is basically a string of gruesome accidents... and since Damien is still coming to terms with who he is, that's all they feel like. They're not murders, they're just accidents. Damien isn't doing it deliberately, he's just wandering through the film being a teenager. Oh, and that's another problem right there. Evil children can be scary. Evil adults can be scary. Evil teenagers with evil teenage angst... no. Teenagers are stupid! They're confused! They're hormone-ridden! It's hard to be scared of someone who's squeezing his spots and shouting at his daddy, even if that daddy happens to be the Ultimate Adversary, Father of Lies.
The film perks up considerably once Damien is reconciled in his mind with being the Antichrist. Suddenly his killings feel like murders and everything feels less random. There's also some good character stuff with his adoptive family. But if the script was going to go down this road, I think it should have gone a great deal further - explore what it's like to be a teenage mass-murderer with enough mental power to snap elevator cables or trigger earthquakes from halfway around the world.
There are little touches. For those who've seen the film before, take another look at "promise you won't talk to him differently or look at him differently". There might be other motives behind that plea.
I suppose you could claim it has a kind of slow-building atmosphere, like Lovecraft on dope. Nevertheless for me a horror movie needs to get me concerned for the good guys and afraid about them. Here they're all doomed. They're spear-carriers. The only audience-grabbing character is Damien himself, struggling to deal with the unfortunate news that he's the son of Satan. I mean, that's a bugger. Could spoil anyone's day. I liked individual moments and some of the deaths were cool, but at the end of the day it's an impressive, stately edifice that doesn't really go anywhere.