I'm afraid I will have to disagree with all of you. There is no good way to say who is the single greatest. Yes, Burns would be the greatest Scottish poet. AND, Fleming could be argued as the greatest Scottish scientist. But I would suggest that you can only take greatest to being the greatest of a catagory, not of everything. To those that are more interested in the arts a scientist would never be the greatest and the same goes the other way.

Just my 2 cents.