I erased my original reply to this in favor of something a little more clear.
I think there are two capabilities that are important for an artist to have. I also think that thinking of it in this way answers a lot of common philosophical problems, particularly regarding the actual definition of art. Okay, that's a bold assertion... but anyway.
First a definition: If you've ever taken an intro psychology, philosophy, religious studies, or probably any humanities course you probably have encountered the widespread belief that we can't actually ever really see the world, all we have is limited sense data that's been filtered to death by our brains, trimmed down and categorized and labelled and fed to our conscious mind in small doses. These small doses, this limited little view of the world, is what I'll call "internal representation" of the world.
The two abilities: 1. Artistic ability - The ability to redefine one's internal representation of the world, probably in some novel way that hasn't necessarily been taught directly to you by someone else. This is a lot harder than it might sound, because all these little things you take for granted about the way your brain processes the world aren't exactly screaming "Hey, I'm just an arbitrary decision made by your nervous system!" or anything, so it's hard to recognize where there is some freedom in interpretation. 2. Technical ability - the ability to manifest this internal representation as something tangible, material - either some work of art, a piece of technology, some communication (writing or speech), etc.
People have these two abilities in different doses. A good artist has both - he can see the world in a new way AND communicate this through whatever medium he is technically proficient with. Someone we might call a technician maybe has no ability to manipulate his worldview, but is skilled at manifesting it in (for example) photography - he takes technically perfect photos with excellent exposure, but they are boring, because they do not show us anything novel - he is simply transcribing an unquestioned representation of the world that his brain fed him automatically, which usually means it's some consensus view of things that isn't going to surprise and amaze anybody. People always have symmetrical faces. Cities are best viewed as rows of tall buildings as seen from a distance. Kittens play with balls of yarn on piles of soft pillows.
On the other hand, there are dreamers, who can rearrange their view of the world inside their heads at will, but aren't very good at communicating this view, probably because they are lacking in some technical ability like painting or sculpture or photography or speech writing.
So the issue of "is it art or not" I guess is still a matter of being in the eye of the beholder. The beholder in this case will say something is art if it communicates some new way of viewing things to him, and it will be nothing but technical tripe if the critic has already been exposed to the artist's particular view of the world. This is why different weird phenomena like cubism and abstraction and whatnot are exciting to people for awhile and then become boring and derivative - the first person to conceive of it (I'm no art historian, sorry) did a literal rearrangement of his own sensory & cognitive processes and then transcribed it and communicated it, everyone since just stole this view and regurgitated it and reinterpreted it ad nauseum and the critics would call it derivative and boring - simply because it no longer amazes them with a new idea of how the world can be perceived.