Peter,
It should be fairly easy to come up with the criteria for a good hole, not that some here would disagree, and all here would disagree to the the degree that it makes for forumula. However, most players would say total visibility (lays out like road map), often from a gently elevated tee. All the actual ground can vary quite a bit, but only a few things - reverse slope fw, 90 degree doglegs, and such - would be ID'd as making a bad hole. There are a few more, I'm sure.
Beyond those items, the easiest part to quantify is a hole that just "feels" awkward. The hardest part to quantify is the "natural grace" good holes have. A good routing can have 18 good holes, a great one needs most of those to have "grace" or natural flow.
As mentioned, I consider variety and close walks sort of second order stuff. We have all those checklists about wind, up and down hill, yardage and dogleg balance. Over the years, I found I picked the best of the dozens of routings based on the best holes, rather than the best balance. A more real question for me tended to be "best holes" vs. "short walks". Even then, I generally opted for the best holes, despite the obvious advantages of short walks.
Routing is an interesting excersize. I have told the story about an architect I know. Basically, he told me that he figured every course had a few bad holes, and his certainly do. Good routing is probably as much hard work, considering options. If you could find out how many routings the gca did, I would bet that more good routings came after two dozen routings than after two.
The best of mine came when I was able to put it away for a week, month, or year. When I came back, things always looked different to me, and I came up with more good ideas later. Sometimes, when there is pressure to get it out in a week, you get stuck on certain ideas (routers block?)
One last note - I have no ideas how you could tell if the gca used the existing land forms "best" or not. In my experience, the question wasn't to use or not use a landform, it was how to use it - backing ridge or fronting ridge, angle or straight, par 3 or par 5, etc. etc. etc. Most good landforms can be used a few different ways, and the choice of how usually comes down to how the holes fit the land, and/or the gca preferences in creating that elusive balance or "ideal challenge".
Another last note from the posts by Hoak and Doak.....I loved a course as a kid that had one crossover, and was sublty influenced to use them as a quirky feature. But, in the main, they really don't work all that well in the circulation of the golf course, and I now try to avoid them.