The most disinterested and careful attempt to measure the scholarly consensus regarding the most important individuals in history in the arts and sciences is Charles Murray's 2003 book Human Accomplishment. His methodology is described in my review in The American Conservative and in my interview with Murray, but basically he's measuring how much attention is paid each name in the leading scholarly reference works in each field.
There's an obvious high culture / academic orientation to the lists, but what scholars are basically interested in is how much somebody influenced subsequent major figures in his field.
To be eligible, you have to have been born by 1910 or died by 1950. Everybody is ranked relative to the immortal who ranks highest in his field. Murray stays away from ranking political and religious figures.
Murray kindly sent me a copy of his database. (And, no, I won't post it on the web without his permission.) I'll put up the most important Americans in science, math, and technology another day. (Briefly, the most impressive American figures in the lists are Thomas Edison, who ties with James Watt for the top ranking in Technology, and Benjamin Franklin, who is the only American on three lists: he's a major figure in Physics and Technology, and a minor eminence in Western Literature.)
I will start with the softer side and come back later to the sciences. Here are the top American names in each category:
Western Literature (Shakespeare = 100)
|Twain, Mark (Clemens)||1835||12|
|Dos Passos, John||1896||8|
Americans account for 58 of the 835 writers who made the grade in Western Literature, or 7%.
Poe seems to be that rarity who reads better in translation (especially in French). Auden is classed as an American because he spent the majority of his career in America, while T.S. Eliot is grouped with the Brits.
Western Painting and Sculpture (Michelangelo = 100)
|De Kooning, Willem||1904||10|
Overall, Americans account for 29 of the 479 Western Artists, or 6%.
This list does not include architecture, so Louis Sullivan and Frank Lloyd Wright are not eligible, nor decorative arts, so Louis Comfort Tiffany isn't either.
I suspect, in the long run, that Eakins will emerge at the top of American painters.
Western Classical Composers: (Mozart and Beethoven tied at 100)
Americans account for 21 of 522 Western Music composers, or 4%. I would imagine Americans do better in Murray's lists of writers than composers because there's not as much of a classical-pop division among writers, so Edgar Allan Poe could do very well in Murray's system, but Cole Porter can't.
Gershwin would no doubt rank in the top 10 popular composers as well.
Western Philosophers (Aristotle = 100)
Americans account for 6 out of 155 Western philosophers, or 4%.
Americans aren't terribly philosophically inclined, but that's not a bad little bunch.
Overall, of the 115 Americans in these four categories, seven are women, with Emily Dickinson highest ranked. There are two blacks, Richard Wright and Duke Ellington.