What makes art, art?

I have seen paintings that took time and effort, that are works of beauty. These painting were valued in the renaissance and early American time periods. Where art was the photography of the day. 

With the invention of the camera, the need for art for viewing people has become significantly less important. We now use art in an expressive and abstract form that can express true creativity.

But is it really creative?

I have seen paintings that are nothing more than a single black line on a canvas, be sold for millions of dollars. While paintings on the street (though illegal in vandalizing) have been often more beautiful and time consuming. 

I agree with Tony Stark in regards to art. In Iron Man 2, he gets a poster with Iron man on it in red, white, and blue. A pop art poster of  himself. He walks over to the painting that according to Pepper Pots is worth a lot of money and is very valuable. The painting is nothing more than a single black bar on white paper. He takes down the painting and replaces it with his poster.

( I tried inserting a picture I had made of a black bar on a white stretch of canvas here. The computer said that the file had to be a video, or image. The computer didn't even recognize the "painting" as art!)