The judgment is based on personal liking and personal taste. For example I may find a painting of a duel more appealing that a field of poppies only because to me the two men involved in the duel invites me into a conversation with the painting of the present and the past. Some ask whether aesthetic judgments are objective, as in science. I think this is true only for an art critic or expert. They see art and judge art objectively, whereas to a common spectator art is subjective.
Art viewed by a common person is judged by taste and personal background.
When a spectator looks at art, he brings his whole past history and knowledge into the art work. He personalizes the art before him and tries to find some meaning from it which pertains only to him. One spectators meaning of an art piece may not necessarily be the same as another person, whether this other person is a brother, stranger, or neighbor. Subjectively looking at art is based on taste. If you think it is a bad painting then it is bad.