Decent until it slips into fringe theories... To be clear, I am not a Christian and have no theological quarrel in this review. However, I still have an interest in religious history. I listen to talks (and debates) about Jesus and the Bible from such scholars as Bart Erhman (Atheist) and N. T. Wright (Christian).
Marketing the Messiah starts off as a good popular-level introduction to modern scholarship about Jesus, Paul, and the New Testament. I agree that Paul was a heavy influence on what Christianity became, but there isn't much debate on that.
The documentary opens by stating that the modern Christmas story is a caricature of what is actually in the Gospels, which is absolutely true. However, I felt that the host did the exact same thing with other topics at times.
There is some decent comedy, though sometimes it also fell flat. I appreciated the use of "Jesus is a Friend" song, which was a minor viral video that was going around the Internet a few years ago.
Despite some minor complaints, I liked the documentary for the most part and would have given it a rating of 7. Unfortunately, the final 20 minutes takes a turn for the worst.
The documentary ends by pushing fringe theories of rejected Bible books (from the late 2nd Century) and the Christ Myth Theory (Jesus never existed). These positions are held by no serious Biblical scholar (Christian or Not).
They spend time supporting the views and give minimal criticism of them. It was a disappointing end to an otherwise decent documentary. I recommend looking up the debate on Youtube between Erhman and Price about the Christ Myth Theory.