The case is if you count or not count Paul's work with the Beatles. Let's face it. Paul's best work was with the Beatles, so if you're counting just Paul's work with Wings and as a solo artist, well of course I would said Elton John. He released a collection of amazing and commercially successful albums between 1972-1976, and sold over 100 million records. He also has the best-selling single of all time (30 million copies) and achieve over 25 Top 10 albums.
In the other hand Paul composed lyrics and music, and Elton is a fantastic music composer but terrible lyricist. Paul plays every instrument known in this world (
) and Elton is just a piano player (but freakingly amazing piano player!).
So, who's better?
I would say Paul. But I love both artists. If Paul's my favourite musician, and Stevie Wonder's my second, I would put Elton in the third place.