Always thought ---

To each their own I guess

Wasn't impressed with George Cs new charector going forward "The Angry Old Man"

Deniro and Pacino have taken over for him

While not a bad movie and definitely the most well-crafted sequel after the original, it has its flaws. Exorcist II is frankly underrated. The movie went about its way to try new things and expand the story that didn't come off as a rehash of the original and I like the sci-fi element it brought. The effects were also good. With some improvement on some acting and story consistency, that one could have really done wonders and been better received. But one thing you can't say about the movie is that was a cash-in. The director went about his way to truly make that movie its own thing.

Now Exorcist III fails a lot because it's not really an "exorcist" story since it's mostly a murder mystery with some catholic ties thrown in. The titular angle comes about very briefly at the end and lasts only ten minutes whereas the original had much more it that took up the entire third act of the movie and the sequel even had moments of exorcisms first with that Hispanic girl at the start, Kikimo in the middle, and then the Regan doppelganger at the end. But hey, the movie didn't even need to have many exorcisms or a lengthy one since it's titled "THE EXORCIST". It just needed an exorcist character as the focus really, which is what this movie needed. Rather than following a cop, we should have followed an exorcist.

Since Blatty was following his Legion book, I'd retain most of its story beats, but I would have made some changes to craft the story as an Exorcist sequel and with better continuity ties. Kinderman can still be the focus, but rather than it being the same one from the original, it would be a younger brother. Dyer would either be played by William O'Malley again or he'd just be a different character entirely. Father Riley would have been The Gemini Killer's dad and be the one to do the exorcism at the end in place of Father Morning....

Part 2 since we're on limited comment space here.

I found the character of Father Riley to be useless so having him be the one to handle The Gemini Killer/Pazuzu at the end would have made his role more important. Never understood the need for Blatty to throw in this priest character o do that without any real development when he could have just made do of the one he already had in the story with good enough development and interaction with Kinderman. As far as him being The Gemini Killer's father, it's established in both book and movie that the father is a priest, but trying to put him in the movie would have left little room for development given the characters we have so far, so changing this to an already established character like Father Riley is reasonable.

Given how awesome Father Morning's actor is in the little time we seen him, I'd hate to ax him entirely. If Dyer had to be replaced with a new character if O'Malley couldn't come back (rather than recast), then the Morning character could take his place with the same actor or the actor could have taken over the role of Father Riley. I didn't care too much for the Father Riley actor so I don't mind if he had to be replaced. Plus, Morning's actor clearly gives off a better presence to carry an exorcism.

The poster makes such a big deal about the steps but the movie does little with it. I would have utilized this more a couple times after the opening. Brief mentions of the events of Exorcist II and the original being set in 1973 (not 1975). Also, Kinderman (now the brother) having dreams of the Gemini Killer and his father trying to exorcise him before his execution, so we see mor of Brad Dourif outside of the cell stuff...

Part 3, the final one.

Lastly, I would have done away with Pazuzu altogether. The demon for one seemed like an afterthought with how we only see it during the climax and not once is referred to by its name other than "The Master". It also rather takes over The Gemini Killer's role with TGK's fate left just not disclosed. Was he still there in Karras the whole time or did he leave the elderly patient's body (disguised as a nurse) after the fight sequence at Kinderman's house? We aren't told this. I would have still had Pazuzu be the one to put TGK in Karras' body, but only have TGK in it all the way though so he has a proper fleshed out arc here and be the one his father and later Kinderman fights at the end. So after taking over the elderly patient's body, TGK returns to Karras' body and the showdown with Father Riley kicks off and the events play out the same as the actual movie.

So that's all I would have done differently.