No one else was going to make that trip for probably hundreds of years. The idea that someone could sail west from the coast of Africa and reach Asia alive was ludicrous. The only reason Columbus believed he could was because he thought that the Earth was substantially smaller than it actually is. He didn't have the provisions on board to make it to China. He was so amazingly wrong and lucky. In the end, he died still believing that his calculations were correct and that China was just a little farther west than he reached. It was only through his "successful" return that other European voyagers would travel to the Americas and connect the world in way that hadn't been seen since Gondwanaland divided. Right or wrong this changed everything everywhere in a historically short period of time.
Does this deserve a day? Columbus day was only invented 227 years ago (the tricentennial of his original landing), largely through the influence of Washington Irving who was trying to give the relatively new country of the United States of America a sense of historical importance. The quadricentennial saw the Chicago Columbian Exposition which changed the way that Americans saw the future of their country. The quincentennial brought the plight and causes of Native Americans (one could say "finally") into the mainstream American consciousness.
Columbus brought slavery, disease, and death to the Americas, but his voyages also inadvertently brought about the Modern Era. Now if you'll pardon me, I need to prepare for November 14th, Genghis Khan's birthday.