When I went into Jeff Sutherland's Scrum Master class, he stated that "The Scrum Master is the most important person in the team", on the Product Owner Training, I heard "The Product Owner is ..." - and during Scrum Developer Training, I heard the same about Developers.
Now, what is the real deal?
Let's look at this slowly.
The Product OwnerImagine you have no Product Owner.
Who takes care of the backlog, who grooms it? Who makes the calls when stakeholders quarrel about the direction of the product? Who communicates the product vision to developers and stakeholders?
Ok, let's make it short. If there is no product owner, there is no product, there is no project. There is no need for a team - so obviously, the PO is the most important person.
Well, that was quick.