Harrison and Ringo were the best pure musicians.
Harrison was clearly the best guitar player compared to John and Paul (bass). If you listen to some of the covers he did of 50s rockabilly songs as well as his work on the last couple of Beatles albums, it's extraordinary.
Ringo as a drummer, was in a class by himself. He never gets enough credit when mentioned among the greatest drummers of all time. Other drummers do acknowledge him but the press and fans don't have the technical knowledge to realize his greatness. He was left-handed but played right-handed. That helped him with skills like the "sizzle-symbol."
I'm still a huge McCartney fan and his real skills lies in writing and arranging. Until recently, I did not realize how limited Lennon was musically. I heard a George Martin interview after his death and he was speaking about Lennon being mostly an "idea man," who was not the most technically gifted artist.