Perhaps you would agree, in return, that while many were the equal of Einstein in their mastery of "the method", none, not a single one, could hold a candle to the blaze of his imagination, at least during his most productive years.

I don't know. Marc Kac has a great discussion of this sort of genius in his book, "Enigmas of Chance." He says there is ordinary genius and magical genius. For ordinary genius, you think to yourself, "On my best day, I could have thought of that same thing." For magical genius, you think to yourself, even after the theory is explained to you over and over, "What in the heck made him think of this in the first place?"

Magical genius is a rare thing, but I suspect it has a lot to do with an abnormal ability to concentrate. There have been several people in history who manifested this sort of magical genius - Gauss, Archimedes, Newton. The book makes special mention of a particular magical genius - Richard Feynman, who died of cancer less than two decades ago. Feynman was a generation behind Einstein, but I suspect that were he not already aware of relativity, he might well be able to reproduce it. This is pure speculation, course. It's not as if I thought that genius were easily quantifiable (by me or by anyone else). Even if he were capable of doing it, there's no reason to whatever to think that he actually would have done so. What is it that causes a person to obsess so about problem? Why one problem and not another? There is no end of interesting questions that one might ask.

I suppose there must be people in other sciences - or even in disciplines as far removed as the fine arts - whose powers of concentration and insight might mark them as magical geniuses were they applied to similar fundamental problems. This is another factor that Kac brings up: Feynman, Einstein, and Godel were all fundamentalists; they were all concerned with the foundational aspects of their studies.

So my reading of Kac (and others) suggests there are at least two criteria such a magical genius might possess:
1. Abnormal power of concentration.
2. Obsessive interest in the fundamentals of a subject.

Maybe I can also add
3. Imagination
4. Intelligence (though I don't think these last two are orthogonal).

I don't disagree that Einstein was a great genius; I just don't think I'm qualified to judge it. Moreover, I'm not sure I would accept anyone else's judgment so far. I'm reminded of a some web pages I visited some time ago in which "some people," presumably experts (at something), reviewed the famous writings of history and assigned posthumous IQs to famous people of history based not on tests, of course, but on various proxies, namely the writings they have left behind. Miraculously, these people have determined that Hypatia must have been smarter than da Vinci or Pascal! Bertrand Russell was smarter than Einstein! And the different estimators disagree - for example, some have Bill Clinton at 180+ (about one person in a million) and other say he was only in the 130s. I saw one once that said Kant was smarter than Gauss. My jaw dropped. My first thought was: this is a joke, right? Then I noticed that these estimates seem to heavily bias in favor philosophers.