Basically a question like this is bond to be really controversial and there is a lot debate even in serious academia about this.

For instance, one of the argument (I think it's by Kenneth Pomeranz) made as that colonialism was key to European industrialization. The argument is that acquisition of land and labor through colonialism produced goods and foodstuff that were "labor-saving" and "land-intensive" within Europe (specifically England). What this meant was that England had both the food security (industries are massive food drains) and and surplus labor needed for industrialization.

The argument is again, pretty controversial and I suspect that whatever conclusion reached probably has more to do with the person's political view than anything else.

This is an immense, complex, and difficult question to answer; when I saw it pop up yesterday, I shied away from it and wondered who would be willing to take it on. Unfortunately, I think the existing answers are quite unsatisfactory, so I'll take a stab at it.

There are several elements that make this a difficult question to answer. For one thing, the terms are ambiguous: what exactly do we mean by "wealth"? GDP overall? GDP per capita? Purchasing power? Standard of living?

And, are we talking about all Europeans, including Russians and Turks? If so, we need to recognize that there are important differentials in wealth across Europe: western Europe is generally wealthier than eastern Europe, but it has not been every thus. For example, at the time Fanon wrote those words, Ireland was extremely poor, as were Spain and Portugal, while the communist countries in eastern Europe are difficult to compare in terms of GDP because they do are not market societies. Even today, a country like Albania is both European and extremely poor.

Are we including European settler colonies in North America and Australasia? While the US, Canada, Australia, and New Zealand are today clearly "wealthy" countries, it is important to note that they became wealthy for somewhat different reasons.

So, just to define whose wealth we're interested in, I'm going to say that we should include Europe, broadly defined to include Russia, as well as the settler colonies in North America and Australasia. I'll omit Latin America, but that is a potential weakness of my argument. (I hope someone can exploit that weakness to give us a more complete picture.) Of course, this opens up the problem that many European countries that are today wealthy did not have significant colonial holdings. While we might point to Britain's, France's, or Holland's empires and see wealth flowing from colony to metropole, it's difficult to see how Greenland could have meaningfully contributed to Denmark's wealth, or Sweden's meager colonial possessions, or Germany's more substantial but short-lived and probably totally unprofitable for anyone's empire. Plus, there are European countries that did have substantial empires but were not very wealthy at the time that Fanon was writing, like Spain and Portugal. And, what should we do with a country like Ireland, which is European but was also effectively a colony of Britain? In 1950, Ireland was among the poorest countries in Europe, but is now quite wealthy (at least in macroeconomic terms).

It seems, then, that one thing we can do straight away is eliminate the idea that colonies (in the past) equal wealth (in the post-1945 period). They clearly do not. We can also eliminate that statement's corollary, that a lack of colonies equals a lack of wealth. Clearly, it is possible for European nations to get wealthy without any direct colonial involvement (Swtizerland). And yet, the pattern clearly persists: "Europe" was home to major colonial powers so that by 1914, Europeans or their descendants controlled something like 90% of the Earth's surface, and today Europe and its settler colonies are most of the wealthiest and most powerful nations on the Earth. What's needed, then, is a broader explanation that can account for the reorientation of the global economy in the modern period so that wealth accumulated in Europe. The best such theory that I know of is Immanuel Wallerstein's "World-Systems Theory."

NOTE: I'm afraid I have to step out now, but I've invested too much in this answer to just give up halfway through. So, I'll stop here for now and I'll finish up later. I'll explain Wallerstein a bit, and try to give some examples of how that played out, drawing on a variety of literature, including but not limited to Ken Pomeranz's The Great Divergence which was, unfortunately, not well-explained elsewhere in this thread.

Not accurate at all. The wealth of Europe was built on intra continental specialization. Amsterdam became rich because it was the warehouse of Europe. Iron from Sweden, Salt from Portugal, Grain from Poland, Wool from England. Because every region specialized in certain goods and traded these, Europe became wealthy. You see this allowed economies of scale. Large concentraded centres of production based on which region was comparatively best suited to produce a certain good.

Because of this specialization, a lot of manpower was available to sail beyond Europe and bring back exotic goods. These exotic goods did not make Europe rich. Spices such as cinnamon were just luxuries.

If you think about the goods the slaves / colonies made: spices, tobacco, sugar. These were all luxuries, but it is specialization that allows a larger and larger part of the population to not be 'just producing food to survive' that makes a country prosperous.

If you look at the Dutch in the 17th century this showed: all these Dutch painters were able to paint all day because of the surplusses.

The surplusses allowed a significant part of the population to pursue science and technological advancement.

Think about it. The Spanish brought back a lot of silver from the silver mines in Peru. This silver actually destroyed their country's economy. You can't eat silver. You can't do anything with silver except create ornaments and jewelry. It caused huge inflation and the decline of Spain in the 17th and 18th century. Their colonial empire gave them no lasting wealth.

The colonial ventures themselves were not all that profitable. The Dutch West India company never made much money of it's colonies. Only it's piracy was really profitable. In the end it went bankrupt.

Now colonialism was mostly a question of prestige and power. Many colonial ventures were loss making, some of them were also profitable.

The German states had no colonies at all and gained significant wealth through the centuries.