It seems as if this question wants a black or white answer, when the true answer can only be grey. There of course will be arguments that Columbus was a hero and that's why we celebrate Columbus Day. There will of course also be arguments that he was the first of many European villains who deliberately exploited then destroyed Native populations. It is my personal belief that both arguments are unfair to Columbus.
What Columbus did by sailing to America in search for a passage to India was inevitable. The social/technological progress that has characterized humanity for all time meant that the large dispersement of peoples and cultures across the world would be eventually bridged. Columbus just happens to be the figure in history responsible for the first official instance of Europeans coming into direct contact with Native Americans. Judging Columbus for the hundreds of years of disease and exploitation, thereby classifying him as simply a villain to humanity, is in realty too harsh a judgement.
Contemporary historians would do well to resist casting strict judgment on the figures of history and their deeds. Life was much different in Columbus' period, with morality and laws of society not as well established or matured as in the current period. What we know of what Columbus did in his own personal life is nothing truly out of the ordinary for his time period in terms of his behavior in relation to strange lands/peoples/cultures he did not expect to find. He simply was a product of his time, like all people of all times, like us. Hence the grey nature of this question's answer.
In summary, Columbus was neither simply hero nor villain. He was the first in a long line of people who would bridge the gap between cultures. The eventual rise of powerful nations, and the eventual fall of native populations, are of little consequence to Columbus personally. It's the differences in human opinion, both in Columbus' time and our time, that make this question impossible to reasonably answer any other way.