I'm not going to lie. Trying to argue against Exorcist being canon worthy ahead of Exorcist 3 is an uphill battle. I don't think I'm going to change too many minds here but I'm just gonna state my ridiculous case and leave it alone.
Friedkin is one of my favorite directors of all time, and I even have tickets to watch the Exorcist and The Devil and Father Amorth with him in May. But let's reality check this one... I think the Exorcist might already be such a game changer that it's almost unworthy of the Canon. I feel like Aliens who might travel to earth millions of years after our destruction and open the files of the Canon to review what movies really changed our society they would see the Exorcist on the list and be like, "Well obviously THAT'S in there."
I think Exorcist 3 is the stronger film in terms of the filmmakers talents. But not against Exorcist... let's be honest this is Blatty's second film. A more fair comparison would be Friedkin's Good Times vs. Exorcist 3. It's not even Friedkin's second directorial effort, we'll give him a hand full of made for television fare. So if we are comparing second films... Exorcist 3 wins easily.
Exorcist 3 is an amazing exercise in what the Exorcist films could have been in a way that doesn't try to copy the original nor does it demean it. (See the multiple prequels for that.) Blatty very cleverly executes his material, his build up and deliveries in a way that just isn't done. Because so many filmmakers have spent lifetimes trying to copy all that is the original Exorcist we have lost a lot of the patience and artfulness to delivering true fear in films. You can argue that the Exorcist is a great balance of tone, story, build up and delivery... but most filmmakers spent their time trying to make a head spin, a demon vomit and a lot of yelling. Exorcist 3 is the rare chance we get to see a genre done really well that is different from the game changer and different than our normal fare. And it's exciting and well done. Imagine the kind of amazing diverse science fiction films we would have if Star Wars never occurred? That is what Exorcist 3 is to the horror genre.
And Blatty is an artist that has made multiple changes to himself as an artist and by all intentions Exorcist 3 shouldn't be any good. But he was talented and lucky. If he hadn't won a gameshow we probably wouldn't have him today. If he hadn't wisely moved away from hollywood romance comedies in the 60s we probably wouldn't have him. He kept his voice throughout the years and when his chances came to direct he was amazing. And I don't know what his experience was but I imagine that two not so well received films made him reticent to make more if not the struggle to be accepted as a director far more difficult.
Blatty was was an amazing talent, without whom we wouldn't have ANY Exorcist and I only get two chances to get him into The Canon and I think Exorcist 3 should be it.... I don't think it will. But if I keep my fingers crossed we will have A Ninth Configuration vs. Good Times sometime in the near future.