Shel's seems like an amiable enough guy. But it seems clear to me that with out the business strategy and vision of Bezos Amazon wouldn't exist. I think this quote summs up Shel's and Bezos's styles succinctly "I am a product of the 60s just like Jeff is a product of the 80s".
I don't think Shel should be considered a co-founder. None of his DNA is imprinted into Amazon. In the end, he was pretty replaceable.