Ridiculous. None of those "many" managed to bring the Western Hemisphere to the attention of the Eastern Hemisphere. Columbus did. That makes him the literal discoverer of America: there is half a world of difference between finding something and un-covering it.
And, like it or not, Columbus's discovery remains one of the most important achievements--arguably the most important achievement--by any individual in any possible history of the world, regardless of what kind of person he was, and regardless of whether you like any particular result of that achievement.
I don't know whether to laugh or puke. Truly astounding postulation