The Scots have been possibly the most successful people on the planet.
Andrew Carnegie, Adam Smith, Alexander Graham Bell, James Watt, David Hume, Robert Burns...
JosF makes a good point, but that's one of the reasons the Scots have been so successful. Instead of being bad neighbors and warring with the English, the Scottish had the good sense to work with English as it became a global power. (or they didn't have a choice if you want to be a dick about it.) However, poorer Scots were also pretty low on the social ladder, so they were always eager to go overseas, and those who did sometimes achieved great wealth or success as soldiers, businessmen, scientists, etc.
The Scottish Enlightenment was a period around the time of the American Revolutionary War where Scottish intellectuals laid down ideas that are still affecting us to this day. Adam Smith, who laid out the American economic policy: capitalism and free trade, was a Scottish economist. Let me give a quote from wikipedia about the Scottish enlightenment which makes me think of why Scots have been so successful:
"Sharing the humanist and rationalist outlook of the European Enlightenment of the same time period, the thinkers of the Scottish Enlightenment asserted the fundamental importance of human reason combined with a rejection of any authority which could not be justified by reason. They held to an optimistic belief in the ability of man to effect changes for the better in society and nature, guided only by reason."
Of course, this doesn't really apply to the whiskey drinking Scotch-Irish who settled Ulster first and then the Southern USA. Scottish people are rebellious, pragmatic, and value both education and strength. They had the first public school system in Europe, and the emphasis on education made Scotland a center for medicine and philosophy.
Germany, especially in the 19th century was also a center of learning, and the great philosophers of the 19th and early 20th came from Germany. Marx, Nietzsche, Hegel, Freud, etc. However Germans do not have that sense of individuality and rebelliousness. I think it is a different type of intellect, not necessarily that one is smarter than another.