It takes the trained objective historian to make the determination of whether or not a long series of events that led to rich gains for the dominator while leading to extreme loss for the dominated was the result of "friend" or "foe." Yet I doubt that many historians today would countenance the extreme oversimplification of complex, enriching and simultaneously devastating historical events, triggered by historical personages, as being initiated by "friend" or "foe." For Europeans, Columbus was a friend indeed as he opened doors of great opportunity from their perspectives. For the inhabitants of continents of the Western Hemisphere, he was surely a foe, an indirect foe since they never knew of him directly.

It is equally impossible to declare "friend" or "foe" while standing on the American continents in the 21st century. If we turn and look to Europe in the East, Columbus is attributed as the beginning of the mighty power that Europe is today. Yet if we turn around and look westward, northward and southward to the American continents, we see the vestige of what once was and those who, having carried the vestige forward, try to keep some of what was smothered still glowing. It's a conundrum: there is no way to answer this question for either way you answer it, you make trivial that which is profoundly important.     

[conundrum: A paradoxical, insoluble, or difficult problem; a dilemma (American Heritage Dictionary)]

At the time of Columbus landing on American shores, European expansion was an enormously profitable and important part of Western culture. Columbus was simply the first person to realistically attempt crossing that ocean; at the time, many people, even intelligent scientists, believed the Earth to be flat and so there to be nothing but empty space beyond those waters. Columbus's voyage set the stage for further European expansion, which had negative effects on indigenous peoples, but it also set the stage for scientific and intellectual expansion, which has benefited everyone on Earth enormously. To say that Columbus alone was somehow responsible for all the evils of European expansionism is to ignore the thousands of other voyages and trips before and after his time. Someone from Europe would eventually have sailed to the Americas and likely had similar effects.

I have to agree that someone would have discovered the land if Columbus had not.  Who discovered America does not really matter.  Different people “discovered” different parts of it.  Some Americans resent Columbus because of his treatment of the natives, while others—especially Italian-Americans, are proud to have Columbus in their heritage.

Columbus represented more than that guy who got lost on the way to India and bumbled his way into another continent. According to a report by the Congressional Research Service, he was supposed to symbolize the hopes of generations of immigrants who came to this country. (See Washington Post)

So Columbus Day is still a holiday.  There are still parades.  People acknowledge that while Columbus did some terrible things, he is still a symbol of hope for many.  If he represents innovation, pride, and discovery, that is not such a bad thing.

Certainly, the Native American populations at the time would have viewed Christopher Columbus as a 'foe.'  If anyone were to read Columbus' journal entries, he immediately begins thinking of ways the native populations might be of use to him:

"It appears to me, that the people are ingenious, and would be good servants and I am of opinion that they would very readily become Christians, as they appear to have no religion" (Columbus Journals).

His first thought is to make them his servants, and his second is to convert them to his religion, and Columbus was not alone in his thinking.  The predominant thought by most of the Europeans was to capitalize on the new found resources of the New World, including potential human labor.  From the human rights angle, the colonization of the New World was disastrous, resulting in the enslavement of large masses of people, both Native American and African, as well as the massive death toll brought on by small pox and cholera epidemics. 

With that being said, the discovery of the New World also brought with it some amazing advances and progress like the Columbian exchange that introduced massive amounts of new types of food and produce to the European market.  Moreover, the new lands created vast social and economic opportunities that stimulated trade and allowed for colonization, eventually leading to the development and creation of the thirteen colonies and gradually, the United States.

I believe the previous answers misinterpret the question, which basically is: were the long term effects of the Colombian Exchange, as instigated by Columbus' presumed "discovery" positive or negative. To that extent, Columbus' contact with the Americas was quite relevant.

As for its effects, they were mixed at best. Obviously, there were numerous ill effects, including the spread of contagious diseases, and virtual extermination of native peoples. At the same time, Europe benefited substantially from the exchange, a fact which the previous responses overlook. The introduction of corn and potatoes to Europe (where they were previously unknown) was a significant factor in improved health and life expectancy in Europe. This in turn led to increased agricultural production, a healthier and growing population, etc. which was a catalyst in the advent of the Industrial Revolution.

As with so many other events in history, the institution of contact between Europe and America cannot be classified as all good or all bad; it was a mixed bag at best. There were many advances to Western Civilization as a result of contact; however it was not without substantial cost.

I agree with the first response, there is really no way to argue that the colonization of the New World was, in the long term, anything but disastrous for Native Americans, though some benefited in the short term by securing European help against their enemies, and through trading with Europeans. I also agree that the effect on Europe was mixed as well. The other region affected by the settlement of the New World and the creation of an Atlantic economy was west Africa. Here again, the effects were mixed. On the one hand, the slave trade enormously enriched African kings and merchants. But of course, that came at the cost of having millions of African people shipped overseas to labor their lives away. For these people, the biggest group of migrants to the New World, it is difficult to see how the development of colonies was anything but catastrophic.

I do not think that Columbus's "discovery" is really relevant.  Regardless of whether he had "discovered" the New World, contact between the New World and the Old would have occurred before long.  Therefore, we should not think of Columbus as particularly responsible for the impacts of his "discovery."

Taking our focus away from Columbus himself and looking at the impact of the contact between the two worlds, we would have to conclude that contact was an unmitigated disaster for the natives of the New World.  It led to the destruction of their civilizations and to the practical extermination of many of their nations.  For people from the Old World, the legacy is much more mixed, but there is no way to argue that it was a good thing for the natives of the Americas.