I'd also say that even if the Beatles formed without John Lennon, their influence would have been lesser. He was the primary force in the Beatles that made people take notice IMHO. His music was a big part but his wit, outspokenness and apparent intellect (as evidenced in the messages the lyrics in his songs espoused as well as in spoken interviews), was the thing that put and kept the Beatles and himself on the map.
Plus, he had a dark side that also helped make him an interesting person, for better or for worse and ironically played a tragic role in his demise. Fascinating stuff!
Lennon/McCartney and LEnnon himself are fascinating topics IMHO. Ying/Yang to the max! McCartney's perhaps lesser public dark side is/was far less interesting IMHO.