The problem, for a lot of people, can be defined as prissy ponciness.. During my last degree course, I had a lecturer in Art History, who was a particularly pretentious idiot. She can be summed up by the following conversation.
Her: "This coke can, if I leave it here, is litter. If an Artist leaves it here, as part of an installation, it becomes Art" [Capital lettesr audible]
Me: "What if I leave it there as part of an installation?"
Her: "It would be litter, not Art"
Me: "Why so?"
Her: "Because you are not an Artist"
The course later introduced the work of David Crystal and Ronald Carter, and Carter in particular addressed my own views on her pompous bollocks: everybody is creative. Genius sits as a cline on humanity; art is something anyone can do, to a greater or lesser extent. The problem is that it is presented as a closed shop, with those on its inside elevated above the plebs.
As an example, I am a writer, according to those who read my work. I am a writer by strict definition--I have thirteen full-length works for sale, ranging from around 50k words to well over 150k. The BBC calls me a writer. I am not a writer according to others as I have not been anointed by any particular commercial publisher.
Here's my take on the 'definition': it is not the name of the creator who determines whether a work is art or not, it is the work. Everyone has their own idea of what constitutes art, and I am not going to stir that pot. I just say that the work should be judged on its own merits, not on any name attached to it. That brings us back to the earlier question about the fake works.
Judge them on their merits, which includes the artist's intent in creating them. Don't judge any art by price, as that is bollocks.
And while I was typing this, Ben T hit th enail on the head.