apparently the Smithsonian agreed to never recognise any other potential first flight pioneer in exchange for the Wright's plane. Dundee claims an early flying pioneer, possibly the first in UK, maybe the world.
http://www.thecourier.co.uk/news/history-2.1462/is-history-right-or-was-dundee-s-preston-watson-the-first-to-make-a-powered-flight-1.718839
Loadsa people flew before the Wrights 'first' flight, including both of the Wrights (gliding). Some of 'em even did so (briefly) in powered craft. The Wrights' claim depends on a few qualification to 'first flight', e.g. powered, controlled, took off under own power. It seems pretty certain that their 'first' flight was closer to achieving all of those at once than any previous flight, but it was just one step among many.
To me, their achievements were significant, but I'm not sure that they made any net contribution to aviation. Their insane patent war* held back the progress of aviation in the USA**, & the world was filled with experimenters & theoreticians at the time. It was going to happen, & soon, whether the Wrights existed or not.
*They claimed that any kind of control mechanism which changed the shape of a wing, whether by warping, ailerons, or any other means, was covered by their patent. Patently ridiculous, since wing-warping & ailerons had been in the literature for decades, had been used on experimental gliders, & there was even a prior patent (British, expired) for ailerons.