What exactly constitutes successful aeroplane?
one that can be controlled.
sure the wright's first aeroplane was quite anaemic but it had in place the fundamentals that were developed into the controllable aeroplane.
all the other "firsts" lacked the ability to turn in a controlled fashion.
it was the wrights who were the first to be able to control an aeroplane in a figure of 8 turn.
you'll note that the figure of 8 turn, demonstrating the ability to control the aircraft, was a fundamental element in the Cramer prize for man powered flight.