A quick stab at it -
1. Ball in the air fun - angles off the tee, interest in approach shots going over stuff and around stuff.
2. Ball on the ground fun - ground movement in fairways, around and on greens. I love to see the ball roll and take the curvatures of the land.
3. Variety - If a course is taking you on some sort of journey, there should be easier parts that need to be taken advantage of, and harder parts that need to be negotiated without giving up too many strokes. There should be up and down and right and left and some sort of ramdomness to bunker placement.
4. An aesthetic point of view - I'm not tied to one look, aesthetically, regarding green shapes or bunker shapes or fairway mowing lines, etc., but I like it best when it's obvious that the architect had a specific point of view that they carried through the course, rather than creating a hodgepodge.
5. Brain and body testing - A course needs to make you think, and also needs to require proper execution. The punishment for failure doesn't need to be mulitple strokes or lost balls, but over the course of your round you have to make proper choices and then make the shots, or watch your playing partners walk away with your folding money.