David,
You ask an interesting question, "Can a case be made that Willie Park, Jr. was the greatest overall contributor to the game amongst architects?"
Certainly a case can be made, but depending upon the individual accomplishments within the overall list, either a good or very weak one is what will be produced.
For example, his accomplishments as a player in comparison to Tilly is night and day, yet it would also be safe to say that Tilly's accomplishments as an architect is even more so. There will be 15 USGA and PGA Championships contested on Tilly courses in this decade alone... how many will be on Willie Park courses?
Tilly wrote two books and his other writings and being the Editor for several journals and newspapers at various times make it almost no comparison to Willie in that one. Tilly also may have been ultimately responsible for keeping the PGA of America from going bankrupt during the Great depression as his Course Consultation Tour caused many pros & their clubs to send in back and current dues without which they wouldn't have survuved. And that doesn't even address the overall impact that the tour had on literally hundreds of courses across America.
Did Willie sketch holes and green sites, etc? Tilly carried a pad and drawing implements wherever he went and spent many hours doing so.
Tilly also taught a number of players. In fact his two most notable "students were were Bobby Jones and Ben Hogan. That ain't a bad resume' for any teaching pro.
As far as I know, Willie never took a single photograph, yet Tilly's work was used by many golf writers of his day. In fact, one newspaper article mentioned that Tilly was responsible for many photographs of golf courses, players and tournaments that otherwise wouldn't have been recorded for posterity.
Although he never made a single golf club, he did save the original "Jigger" that Stewart cast. It came out of the mold with a slight imperfection and Stewart decided to throw it away. Tilly convinced him to give him the head and had it shafted and used it for many years. In fact, I believe that it is with his set of clubs that one of his granddaughters still has.
So, how can one compare? In Willie's day he had less opportunities to affect the game on every level that Tilly did, while today's architects, in many ways, have fewer ones as well.
For example, can you picture Tom Doak attending tournament after tournament lugging around camera equipment to take photographs for himself of the course and players? Even if he so dersired, unless he was a recognized member of a media outlet he would never be granted credentials to do so. So there is one area where a comparison would be unfair to Tom and other architects of today.
Now I bring all this up not because i think Tilly had the greatest impact, but rather to make the point that clearly defined parameters need to be established before any fair comparisons can be made for architects from so many different eras.
For his time and opportunities I think it is safe to say that Willie made an impact on the game that is still felt today... and that alone is an amazing accomplishment!