Here's another question:
Which of these two paintings do you think you could paint yourself?
I do not think I could paint pictures similar to either, but I hesitate to draw any conclusions from that about their quality. I used to apply that question as a criterion of quality in music but have long since abandoned it because I do not think my own ability or the lack of it has any bearing on how my brain perceives art.
This is particularly true with music, because all music is completely abstract anyway, without any concession to an external reality. Any meaning of music is imposed by my own mind when I hear or play it. This is not quite the case with painting and literature which can depict a common, external reality. Abstract painting and sculpture, and writing such as Joyce's "Finnegans Wake", largely render the observer or reader free to make his own meanings and associations. This is an immensely liberating experience.
I have a personal connection with this because my father was a very highly skilled traditional woodcarver. In the early sixties, the Auckland City Council bought Barbara Hepworth's "Torso II" for a considerable sum for the art gallery. There was a tremendous public stink about it, with local dignitaries saying it resembled everything from a discarded car part to a cow's backside. Applying the "I could do it" criterion, Dad commenced making abstract wood sculptures as a joke. After a few months and many carvings it wasn't a joke any longer. He declared he suddenly understood what Hepworth and others like her were getting at, and it gave him much pleasure for the rest of his life.
Therefore, whether abstract or realistic, the only essential for me is that the work of art has beauty, or more correctly what I consider beauty, in the broadest possible sense of that word.