In the 60s, it was Paul. These days I think John really made a bigger difference than any of them because of his GREAT voice. Paul had a great voice to and was a better songwriter but John had a once in a lifetime voice. I think John was on track to become a deeper thinker than any of them when he was killed. Paul has just lost me on some things. George always seemed a bit off kilter to me and I never liked the way he looked (not that looks should matter)...
Ringo is magic in most every way. He has always been funny, has always kept a low profile, always done his job and done it well.. and he has always been funny. I know he ent straight to NYC when John was killed to console Yoko. As a person: Ringo. Songwriter: Paul (Yesterday: acoustic guitar and vocal... can you imagine when he came into the studio and performed that song the first time?) .
Singer/whole package:
John. Though I absolutely HATE the song Imagine... go figure.
J