Officially, Ringo is the most successful as a solo artist in terms of sales - this is “Final Jeopardy “ territory- remember bulk of Paul’s work was as a member of Wings, or under Paul McCartney and Wings, not technically as a solo artist. George needs to be given kudos though as he certainly proved himself as a songwriter on the same level of John and Paul. And he co-wrote a lot for Ringo, credited and uncredited.