Usually when a movie is made from a book people tend to say "The book was better" It is rare when a movie made from a play is considered better than the play. I find it interesting that in these examples the less literal medium is often consider better. However, when looking at paintings a number of people seem to think that the more literal the interpretation the better. While paintings that interprets life literally can be very good, there is a real danger that such a painting becomes too detailed and in fact look too much like a photograph ( by the way some very realistic paintings are done by projecting a slide on to a canvas and painting on that).
While a photograph can be a work of art in itself, in my opinion a painting should bring something different to the viewer, otherwise why not just take a photo? A good painting has to have elements of design that makes it good. These elements include light and shade, composition, and style, the unique vision and technique of the artist. Photographs need these elements too, but the last element, style, is quite different for a photograph than for a painting. That is what separates a painting from a photograph, for while a photographer might adjust things like focus and exposure to create a sense of style every stroke that an artist paints creates the style. It is that over sense of style that I look for in great paintings and not a photographic realism or attention to detail.