This movie followed in the wake of The Exorcist, and was immensely popular. Movies about apocalyptic disasters and demonic children were hot box office commodities in the 70s, and The Omen had both topics covered. However, The Omen was also an intelligently scripted, beautifully filmed and very suspenseful thriller to boot. It wasn't just a rip off of The Exorcist; it had its own story to tell, one taken from the Book Of Revelation, the most grim and frightening book in the Bible.
The characters played by Gregory Peck and Lee Remick may be the "beautiful people" - rich, powerful and privileged - but they are still real people, and quite accessible. Kathy is a strong but emotionally fragile woman who seeks help from a psychiatrist. Robert will do anything to protect her from heartbreak and pain. It is their devotion to each other that makes this film so tense as we watch their lives unravel. Robert thought that by taking Damien in, he would simultaneously save his wife from grief and give an orphan a home, but the road to Hell is paved with good intentions, and in this case, that road is very real.
David Warner as Jennings and Patrick Troughton as the cursed Father Brennan also win our sympathy as the ill-fated men who try their best to help Robert. Billie Whitelaw as Mrs. Blaylock is evil personified. We like her even though she's Satan's minion - it's her wicked, secretive smile and the fact that she'll do anything to protect Damien. Even Damien himself has our sympathy, even though little kids in tiny little suits are just really upsettingly scary. It's not Damien's fault that he is what he is - he didn't ask for this dubious honor, after all - and when he begs Robert not to kill him at film's end, it's hard not to feel sorry for both of them.
This is a great film, filled with vicious Rottweilers, nasty deaths, powerful music and great performances by the entire cast. Should not be missed by film buffs in general and horror fans in particular.