1) Fun.
2) Beauty.
Both are vague, so I'll elaborate. For Fun, I like quirk, contour, and topography changes. On relatively flat terrain, I want fairways to have some rumple or movement, greens to have personality, and the overall course to have variety. I want to be able to remember each hole. (I've never played Firestone, but I suspect it would bore me silly. But this is pure speculation.)
For Beauty, I am equally happy with beautiful surroundings or lovely aesthetics within the course itself -- well-framed views from the tee or well-framed greens as you approach. "Framing" can be accomplished by bunkers, mounds, the general roll of the fairway, trees (preferably in moderation) or even by distant hills, and it doesn't need to be symmetrical. I like good, strong visuals -- landmarks large and small that lead the eye towards the destination, even if there's deception involved.
My home course is a 9-hole Raynor that is rich in all of these features. I've been lucky enough to play a few world class courses, and among them my favorites are Cabot Links, Royal Dornoch, Sleepy Hollow, and Prestwick. Each of them occupies a different place in my two dimensional Fun-Beauty grid. Prestwick wins for Fun, Sleepy Hollow for Beauty, but Cabot and RDGC probably take the prize for the best combination. My sample size, however, is small, and may remain so.