On a frigid, blustery day here in NJ, I'm giving serious thought to this question.
With eighteen great holes and everyone's favorite an exercise in subjectivity, it's a tough, if not impossible task to single out one hole that is "best" or superior to the other seventeen.
For me, #15 is my nomination. Why? Because it is undeniably one of the world's premier par 5's. Why? Few, if any other par 5's provide the strategic interest values on every shot, protect itself from pure distance and promise a scoring disaster if a player loses even an iota of focus.
The tee shot is a pure forced carry of probably 170-190yds, albeit to the widest portion of a fairway that begins it narrowing funneling from there. The hard cant of this fairway complicates things. A shrewd player, having hit a good drive, needs to hug the left side where sequential pit bunkers and overhanging branches promise to produce at least a bogey or more. A well-struck second shot will tumble down to the right third of fairway (worse farther right is yet more stifling bunkers, rough and some branches) leaving an awkward off-cant semi-blind green that is tilted heavily left-to-right and back to front. Any approach coming up short will find itself rolling back and off to the right 20-30 yds. Long or hard left is even worse. Good luck holding that green coming from those places under usual conditions. Simply put, it's a demanding penal hole, yet eminently satisfying when played smartly.
The hole is visually very attractive and seductively in front of you. Distance must be measured equally with accuracy. There is no room to "just bang it as hard as possible." It's an unrelenting, yet beautiful test.