What sets fine art apart?
Short Answer: quality in subject, materials and process.
Quality in Subject
Quality of subject is the most subjective, no pun intended. Who is to say whether one subject is better than another?
I'm certainly not qualified to say. But luckily it's subjective. I find that if you are aiming for truth no matter how simply, someone else will see it as true and valuable as well.
My work is also centered around beauty and realism and so it is very easy for me and anyone else to tell whether my work succeeded in high quality of subject.
Quality in Materials
Quality materials are the easiest to fall in love with and the most expensive to commit to.
I've completely fallen in love with the tools of the trade: the way paint comes out of the tube and rests on the painting surface, the texture and feeling of expensive watercolor paper.