I can't see a classical top ten list not comprising of

Ali(1 or 2)
Robinson(1 or 2)
Willie Pep(3 or 4)
Henry Armstrong(or 4)
Duran(6)
Ezzard Charles(7)
Benny Leonard(
Gene Tunney(9)
Joe Louis(5)

The last person could be anyone, but they hit the top ten pretty well except Jack Johnson and Dempsey IMO. I would probably use Conn.