It's a combination of all four of them. Food is meant to be attractive in every way, taste wise, appearance wise and don't even get me started on the smell!!!! Nutritionally, it should also be worth its weight, so I don't think that there's any one factor that determines whether or not food is "good food".

The best meals I've ever eaten had me salivating from just the site of it and I was already booked when I got a whiff of it. The taste is of course slightly more important than the others seeing as it's going into your mouth, and if it tastes great and holds back on the calories then thats good food to me!!!