Great topic. For me, what differentiates a truly great golf course, from a mere mortal golf course, is how the whole of the 18 relate to each other, with similar themes, looks and a consistent degree of difficulty, hole to hole, throughout the course.
Shinnecock Hills is a fantastic example. Similar themes of false fronts, great speed slots, deep bunkering and fast playing conditions and a consistent topography, throughout. The consistency of difficulty is remarkably true. There are easier holes but none so easy you let your guard down but none, save for the par three 11th, where you don't feel par is a fair and gettable with good, solid play.
Compare that to NGL next door where pure golf gives way to quirkiness and almost "smirky,sense of humor" design characteristics. The degree of difficulty of the holes varies, widely, luck plays a much bigger role.
Similar neighbor example is Muirfield and North Berwick. It's almost like if the courses were movies, Muirfield would be a drama and North Berwick would be a comedy. Both have such stature in the game, yet they are so different. I wouldn't consider going there and not playing both, if given the opportunity to play one twice. But in the end, I prefer the drama and rate courses higher, in my mind, who balance the hard/not too hard in a consistent, recognizable, unique to that course, sort of way. At Muirfield, it's the consistent demand off the tee, the genius bunker placement waiting to punish any mistake but there is a bit of width and a way to shoot a low score if you strike it well. And strokes aren't taken from you due to excessively difficult greens. That's the worst design element of all, imo.
It's fine if its at Augusta where you can hit it anywhere, almost and still get around. The opposite is Bethpage Black where the greens are maybe the easiest of any rated course in the world and they should be. The challenge, tee to green is remarkably consistent as are the greens...great course. What I can't stand, more than anything in golf design, is hard tee to green holes with difficult, sectioned green complexes. There just aren't enough scratch players out there, capable of throwing the darts, hole after hole, to warrant building them.
So, for me, to build a really great course...my primary theme would be to achieve a test that is stern, hole to hole, with no let up but not have any holes that cross the line into too difficult. Fair green complexes. My list of fun features I would look to incorporate, to give the identity to the course would be, speed slots (!!!!). Most fun feature in golf, imo. I would build as many as six into the course, three would be pretty easy with tougher green complexes and the other three would be angled, requiring a shaped shot with absolute death for the missed shot, either into bunkering or tall grass. If executed, the birdie becomes more likely with a short, wedge shot in.
Obvious and viewable false fronts. Another really fun design characteristic. I'd have six or seven of them, all perched in a way that the player really sees the shot, the danger and when he comes up short, the sight of the ball rolling back and the visual of the next shot, the dreaded, pinched 35 yard wedge. It's such a much more fun way to take away strokes around a green vs. greens that have positions where two puts are not achievable or even a traditional bunker shot.
And I'd move dirt to achieve it. I'd rather have some manufactured elements that make the course more fun vs. being stuck with the limitations of the land as it is. Obviously, the goal is to make it look as natural as possible but those magical sights where it all falls into place are just too few and far between.