I've been thinking a lot lately on what makes the general public, all of those lovely possible art buyers, go from "oh, isn't that great" (and then walking on), to "Oh my God, I have to have it" (and out with the wallet). For me, there seem to be three main types of visual art (not including photography).
Firstly photo realism/botanical type art, where the artist is basically relaying what they see in realistic detail. This, if they have the technical skills, is an almost factual representation of what they are seeing. To me, this is like a conversation where the artist says "This is what I see and exactly the way I see it" - end of conversation. If the other person has seen the exact same thing, they may agree, but their input is not really necessary.
Secondly, impressionistic/semi abstracted art, where the artist paints, draws or otherwise in a manner that leaves a little to the imagination, where the eye of the viewer must fill in a little, but by standing back, the viewer can see the image that the artist is seeing/feeling. The conversation would go "This is what I see and this is how I feel about it, do YOU see it? And how do you feel about it?" where the viewer is invited to identify with the artist and art because they have invested imagination in the "filling in".
Thirdly, purely abstracted work. This kind of art means a huge amount to the artist, involving heart and soul, and often joy, tears and angst. But to "Joe Public" the puzzle of it all is often just too much effort to decipher and thus to identify with.
I know a lot of artists will probably disagree with me, but this is my theory... I DO like to think about the way things work, and what makes people tick. I indulge in some of all of these forms of art as the mood hits, but I know which one seems to be the most successful.