In my opinion, there is no commercial art. When you produce something with the intention to sell it, it is a product and not an artwork.
So for me, the purpose is the deciding factor, if something is art or not.
As an example:
The music industrie vs. homemade music:
The music industrie engineers songs on purpose. From the start, the songs are written for specific customers. Then to whole production uses techniques to create a product for these customers. -> Product
When someone is expressing his feelings into music, writing a song for himself to express them, it becomes art. The best thing that happens to music, is if untrained people sit in front of instruments and try to get something emotional out, without using all the patterns used before-> Artwork
So imho commercial art is a product and no art in the sense of art. For me art is the expression of emotions and creativity without knowing exactly what you do.