With sincere respect (I mean it) for Beatle fans younger than myself (dirty old man), your appreciation of the Lads is based on having their complete collection of tracks right in front of you. For someone like me who experienced the Beatles back in the day, we were always waiting for the "next chapter", as it were.
Paul has shown throughout his career that he has a wide variety of vocal styles he can pull out of his sleeve. There's a huge difference between "And I Love Her" and "Long Tall Sally", but he did both extremely well.
On "Lady Madonna", Paul rolled out a new voice. He gave hints of this voice on the BBC "That's Alright, Mama", but most of the world didn't have access to that track back in the 60's. Anyway, when I first heard "Lady Madonna", I was fooled. I thought it was Ringo singing. No, seriously. Granted, Ringo's natural singing voice is "tinny", but with a bit of EQ, it can be adjusted.
Paul would go on to use that voice again on later tracks, but "Lady Madonna" was the debut of THAT voice.
So I was thinking: What other singers have Paul's ability to sing with many voices and do them all convincingly? I'll name two and throw it out for other suggestions.
1. Billy Joel. I haven't read enough about Billy Joel, but I'd be willing to bet he modeled his singing after Macca intentionally.
2. Elvis Presley. Compare pre-Army Elvis to post-Army Elvis to Vegas Elvis. The big question is whether he could dust off pre-Army Elvis and sing that way again.