I have been a psychologist for a long time, and have been pretty much at the top of my field for much of that. I have met Jordan Peterson personally, we have spoken on issues of PTSD, I have listened to his lectures and read his books.
(I am the tall one, Jordan Peterson is cuddled up to my wife)
I would rate him as a Master Clinician, with one of the most effective interventional styles I have seen; anyone would be fortunate to have him as their therapist.
As far as credentials go, he was a Harvard professor, tenured full professor at the University of Toronto, which is the #20 best University in the world according to the USNWR 2019 global rankings. Google Scholar places him in the top few percent of all research psychologists in the world, as was pointed out in a comment below Google Scholar places him in the top 50 most cited clinical psychologists, of all time, worldwide:
https://scholar.google.com/citat...
He has sold 3 million copies of his book 12 Rules for life, which makes him the best selling author in psychology for this decade, and in a very tiny handful of successful psychologist authors.
Lastly as a man who has met many famous people, including three Presidents of the United States, and many people trying for that job, I have shaken hands and looked into Jordan Peterson’s eyes, watched him interact with others, and I judge him a good man, a kind man, patient and respectful, and a man who tries to walk the walk, not just talk the talk.
From any objective and reality-based standard, he is a good psychologist, absolutely.