The weakest one IMO
I actually saw the 3rd one first. After comparing it to the other two, I found this one to be somewhat slow and the acting less compelling. The first one had the whole new novelty going on for it and that iconic body of Micah being thrown to the camera and the third had more full throttle scares from the get go. This one took a long while for the action and scares to get going. The acting also seemed unconvincing. Even the supporting actors in the third one were convincing. The third also felt like an homage to Rosemary's Baby with the whole witchcraft cult society being behind the possession.
I'm interested to see in what direction they go in the fourth installment.