The short version: the Spanish got here first and dominated the scene for most of the sixteenth century, with a supporting role from the Portuguese (who have only the Pope and absolute misunderstanding of geography to thank for the popularity of their language today). They wanted gold and silver — they found quite a lot of it and sat fat on their riches for a long while. The mines in South America allowed the Spanish to surpass their mercantile competitors in exporting money, but it also had two related downsides: one, the conquistadores established an empire that was wide-ranging but shallow, eschewing agriculture and concerted European settlement for extractive industries; and two, the abundance of specie in Spain gave little incentive to develop their domestic economy. There were nearly always more men in Spanish America than women, resulting in the creation of a large mestizo, or mixed, population rather than large, European-dominated settlements. Religion became a major side project of the invaders, but importing priests also does little for the gender ratio or the establishment of stable families. The Spanish were never very well rooted in the New World and when, in 1588, the Spanish Armada fiasco demolished the image of Spain's invulnerability in the Atlantic, these weak foundations were revealed. The English and French began to lose their inhibitions about colonization, and Spain's eventual, nearly total evacuation from the New World had begun.
Jamestown came in 1607 and Quebec followed in 1608. The early histories of these settlements are full of misery and failure. Ultimately, the French failure in places like Canada, Acadia, and Louisiana was more consistent than that of the English, who also experienced plenty of starvation before they figured out subsistence and commercial (tobacco, rice) cultivation. All colonial projects depended for their survival and growth on political stability in Europe, of which there was rarely much. War prevented supplies from reaching Walter Raleigh's early settlement at Roanoke in the late 1580s, and the residents were discovered to be missing almost completely without a trace three years later. In another example, lack of attention from the crown and capitalists, along with political upheavals - both international disputes and internal religious conflicts - continually foiled French attempts to prosper in Canada. In the 1620s the distraction of a new war with England cut the last settlements in Quebec off from supply convoys, forcing Samuel de Champlain's tiny settlement to surrender to the English after getting scrawny from foraging in the dirt.
But practical misfortune and international intrigue were not the only factors defining success and failure. The French approached North America in a rather different way than the English. As different parties made their intermittent attempts at serious settlement in New France - venture capitalists, the church, the crown - traders and explorers were simultaneously venturing throughout the continent, trying to cast as wide a net as possible. The authorities were annoyed by this overreach, which saddled them with even greater burdens of territory to defend, but they could do little to stop it. In any case, trade in furs (essential to the unstoppable beaver hat craze in Europe) created a colonialism characterized by dispersed settlements and networks of relations with Native Americans, who were cooperative but also rightly suspicious of the French throughout. The fur trade mattered to the French for political and military reasons as much as economic ones — they used control of strategic points along the rivers of North America to secure their influence throughout the continent. As WJ Eccles observed, "New France was, in fact, a river empire."
By comparison, the early English colonists clung to the coast, built farms and often traded with the inland Native Americans through intermediaries. Here too inward adventures were difficult to contain, as resistance to the Proclamation of 1763 (which attempted to limit English expansion) and the whole history of the United States would eventually show, but the English seemed to have adopted a somewhat more sedentary, rooted pattern than their French or Spanish competitors. The English experience of "colonization" in Ireland had taught them to crush different, inferior cultures (indeed, people of lesser "race") and establish culturally homogenous communities of their own as beachheads of conquest. Historians have suggested that this lesson shaped English attitudes in North America. Their pattern of fixed settlements of Europeans appear to have practically succeeded, making more food and better goods, than the open-ended relationships and networks that the French employed with Native Americans. The French project contained basic contradictions — they might seek advantage by cooperating with (and trying to manipulate) Native Americans up to a point, but their interests - that of an expansionary foreign power with a totally different culture - were antithetical to the interests of Native Americans in the long run. The English did try politicking among the Native Americans at times, but their policy of total intolerance and steady, incremental destruction of neighbors seems to have succeeded, judging from the ongoing string of French military misadventures that obliterated their North American empire.