Given my limited experience to date (19 on site, 9 researched) it might well be Donald Ross. I may be wrong because my sampling is rather small so I remain open-minded that I may be in error.
I still say this knowing how much I admire Charles River, Pinehurst #2 (it took some time), Pine Needles and Southern Pines (which were really nice surprises this year). I highly regard LuLu and much of Gulph Mills (understanding the Maxwell changes). I think all the greens at Aronimink are wonderful and I like quite a number of greens at CC York.
I take it for granted that he has a number of great courses I've never seen including Seminole, Sara Bay, Plainfield and a number of his Massachusetts and New England courses. I look forward to seeing/playing many such courses in the future. Ron Forse keeps telling me about a lot of Ross courses that I need to see including Mountain Ridge among many others.
Yet for all of that, aren't there a rather large number of mediocre to below average courses? Should they be disregarded because he was spreading the game of golf and he was just laying them out en masse?
Three reasons for my selection of Ross as most overrated:
1. The vast majority of his courses had little staying power. He didn't seem to foresee the future of golf and account for it. A number of his courses were remodeled within less than 10 years of their construction; including seven by Flynn (a high percentage of Flynn's redesign work).
2. His routing style was rather one dimensional. Tom Paul has noticed his propensity to have high tees, low landing areas and high greens. I've seen this over and over. Well, at CC York (Craigh Disher and I were there today to study not play) he did this a lot and missed out on some really great topographic features and the course, in my mind, did not make the best use of land.
For the Flynn book we're just going to stick to a comparison and contrast of the routings and demonstrate routing tendencies. But here I will say that Ross did not come up with as interesting a design nor does his stand the test of time as Flynn's would have. Not only that but Flynn's routing would have taken the golfer to interesting spots with great overlooks or natural settings for walks, tees and green sites in and across ravines that Ross simply avoided because the topography got a bit complicated and the holes were possibly too difficult for a membership that did not want such a test of golf. Maybe Ross gave them what they wanted, but it was a far cry from what the terrain called for.
The Ross/Flynn analysis will be of great interest, I feel. Bob Crosby, Scott Nye, Craig Disher, Tom Paul and I are collaborating with some great input from Rons Forse and Prichard (The Philadelphia, DC, Atlanta School of Golf Research) on the chapter and it will be a highlight of the book.
3. Ross's greatness is established by a relatively small number of courses in his overall portfolio. Are many of his courses disregarded in favor of his best efforts? I think so. Put it this way, do you think his HR to at-bat ratio is poor compared to other architects? How about his batting average? Quite a few big game-winning hits, but are they enough to place him at the apex of the pyramid?