Elvis and the Stones are tied for top honors right now.
I don't know if I'd be much better off voting for my "favorites". I guess I have a more technical ear for music. I mean, I not only listen to what just sounds good, but also listen deeper for things that really are different...an odd timing, a strange chord progression, maybe changing times within a song. Techniques of guitarists and drummers particularly catch my attention.
But so do harmonies and lyrical content. That's what made it so difficult for me in considering a lot of the bands and groups. Like Joni Mitchell. Love her lyrics. Same thing with CSNY. On the other hand, Hendrix: Loved his technique but couldn't much get into some of his lyrics and especially not his vocal quality.
I think that's why I've always loved the Blues. There is continuity to it. A "formula" if you will. But also liked a lot of the lyrics because in so many cases, the story or themes were personal to me.
It's for all those reasons that I can't be disappointed in ANY of the artists we've considered but go insane when I have to eliminate someone from my list. They ALL had a LOT going for them but how do you say "THIS one contributed more to Music Culture than THAT one?" It's both a win-win and a lose-lose!