In a truly 5 course, I want many things. I want to have a wide variety of shots off the tee. Left, right, tunnels, bombers, water carries, uphill, downhill. I want to see bad shots punished off the tee, where par is "saved" rather than settled for. I want to see holes where a good golf shot is necessary, and allows for score seperations. Basics like baskets in good condition, teepads appropriate to each hole, and signage cannot be ignored. Spit and polish is necessary. Our sport thrives on foliage, but it should be trimmed and dare I say, manicured. It should be obvious that love and care go into maintenance, and not just "eh, good enough".
I want to walk out of the car and know I'm near a course. A pro shop is not necessary, but at least a shelter/bulletin board near the first tee helps to serve as a staging point for events. Restroom facilities, trash cans, and a charcoal park grill can help TDs run events. I want the facility to feel like it is catering to the sport, instead of just abiding it.
I have been involved in the sport of Golf for over a decade as a worker. I caddied for nine years on several courses, and have performed nearly every job one could have on a golf course. One thing I have taken away from the game is an appreciation of what takes a course to the top level. The only thing more important than what's on a course, is WHERE is the course. And by that, I want to see great views. I want personal touches that set the course apart. I want a "Pebble Beach Hole 8" signature hole that sticks in your head after the round, the next week, the next year. If I have to think hard about what makes the course great, it won't be getting a 5, unless I'm just trying to single out the very best thing.
To get a 5 from me, you're going to have to "wow" me. But, I'm just some guy on the internet. I don't think my standard for a 5 is very attainable without a dedicated club paying high yearly fees, on a private course. I think these may actually happen within my lifetime, though.