I don't know how good it has to be, on anyone's "scale" ... but I have to enjoy playing it (because of the shots allowed and/or required, the variety of hole locations, the pleasantness of the walk, the beauty of the surroundings -- not to mention the practice facilities) ... and it can't have any single hole that I HATE and dread playing every time I come to it.
I joined a club a year ago, for the first time, because it met all of those criteria, in spades, and -- unlike a few other Twin Cities courses that would meet all of those criteria, (1) it was convenient to home and office, and (2) I could afford it.