Good = A designation for desired attributes within a specific culture at a specific time
Art = A creation that evokes emotional interest
“Good Art” is when you create something that evokes emotional interest and is widely accepted as desirable throughout a specific culture. Lets break this apart:
Good art is not completely relative, otherwise, we would have no concept of “great works of art.” The Sistine Chapel, V-J Day in Times Square, The Dark Knight. When you target your culture and time period, you have a quantifiable ruler for quality. Was the Dark Knight made with the highest quality scriptwriting, cinematography, and acting in any movie ever? No. But if you ask an American if the Dark Knight was a good movie, they would answer with the knowledge that most people say yes. Same goes for Eisenstaedt’s photo and Michelangelo’s ceiling.
If art was unemotional and just a set of standards, the V-J photo would have been widely ignored because there is motion blur and film scratches. The sistine chapel ceiling would have been painted over because more talented artists came after Michelangelo. Heath Ledger’s death was tragic, but it undoubtedly increased the emotional interest in the movie because he literally gave his life to that role.
Good art happens at the crossroads between what your specific audience deems as desirable and what evokes emotional interest.