Both extremely talented in different ways and it's not fair to say one is more so than the other.
Elvis was by far, the better performer and singer than John, whose voice is addictive but not as good as Elvis'.
However, John was the greatest songwriter the world has ever been blessed with. I adore John and I can't express how much - he has been one of my all-time music icons forever and I love what he made the Beatle's into, and I love his solo work even more.
But Elvis' talent is not to be underrated.
I think that shows they are equal. I prefer John 100% but I have the utmost respect for Elvis. What he did for music will never be topped or seen again. I think that in the Beatle's John was kind of restricted as to how unique he could get. When he became a solo star, wow. I still get chills when I hear Beautiful Boy, Imagine and Jealous Guy and Woman...
What John did which was more inspiring than Elvis, was dedicate some of his songs to charity and peace (Power to the people, Give Peace A Chance...) so I prefer him more as a person too.
But please don't underestimate Elvis' talent. He is still the King and always will be.