Paul McCartney is one of the kings of pop (if so inclined) but
John Lennon is an Icon. Lennon could claim status as The King of Rock & Roll in my opinion. He was the main lead vocal, front man and songwriter of the Beatles, and all of his solo material is a must own, especially by a music enthusiast. As well as McCartney's, George Harrison, and Ringo Star's solo work. Harrison is considered one of the best/influential guitarist of all-time and some of his (Harrison) solo work is outstanding . But I think John Lennon is on a level above them all as an artist, activist, personal life, whatever? His single Imagine resonates so loud while the song musically is simple and easy to play.