I watched the whole movie of Exorcist III and there is a jump scare just before that scene - and you even know it is coming but somehow I get the chill feeling from that scene.
The main thing is the slow pacing - very deliberate and the original Exorcist also shares it. Thus I get how some would say it is 'boring' especially compared to a fast-paced horror/psychological more modern thriller like Seven.
I can see with the Brad Dourif scenes how it would have gotten Jeffrey Dahmer 'in the mood' as Dahmer admitted. I think in a way Dourif is more intimidating than Anthony Hopkins in Silence of the Lambs - even without controlling invalids and so forth like the nurse attacking his daughter at the protagonist's home - he has a menace to him whereas the effete stage actor feel of Hopkins takes away from that aspect in my opinion.
In terms of direction in terms of cinematography with both Exorcist and Exorcist III I do think they go for cleverer transitions and foreshadowing than in the Omen - apart from the death scenes - I like but has largely very traditional, conventional staging. Both incidentally use the name Damien - for the priest in the Exorcist and the antichrist in The Omen.
The Omen which I also watched about half of the other day seems to be one mistake after another - one Peck odd misstep after another -
1) just taking a kid from the hospital to replace his son who died in delivery without any records
2) taking in the evil nanny without checking with the agency
3) not listening to Troughton's priest till it's too late
4) not firing the nanny on the spot for the dog
5) acting all paranoid at the end when if he had not sped or panicked he could have gotten away with it
Still I like it though for the aforementioned closer style with Italian gialli and Hammer type horror which I have really grown to appreciate over the last 5-6 years.