Choices created by half par holes help prolong interest and increase appreciation over time.
Short par fours and reachable par fives are the obvious ones -- how aggressive you are on a given day will depend on wind and weather, pin and tee locations, your score and swing for the day. But long threes and long fours also add interest -- do you take them on or play safely for bogey and so on.
Not only do these types of holes add interest to every round, but you learn more about how to play them each time -- what works and what doesn't. And so the course gets better by revealing more subtleties, subtleties that can be different for each player, reflecting the individual strengths and weaknesses of their games.
The only feeling in golf equivalent to taking a chance and pulling it off -- by reaching that par 5 in two, say -- is making a hard fought par on a tough hole by thinking carefully and pulling off a couple of clutch, if conservative, shots.
I like courses that offer both these experiences. They tend to have the most longevity for me.