All great paintings have strong abstraction in their work that is never obliterated by too much rendering. This is not to say that you can’t render something and still have a strong under-painting, because you can. The best realists have strong non-objective qualities to their work. It is mediocre painters that use rendering and over-modeling of the forms to try and mask their inabilities as an artist.
A great painting should work on a number of levels and one of the most fundamental levels is the nonobjective beauty of its components. These are value pattern, design, color harmony and shape. These things do not depend on the representation of some thing to be beautiful. You often hear artists praised for just one of these fundamental elements and rarely all of them. Great artworks have a synergy of idea and application that work perfectly together showing no weak passages to deter from the overall effect.
The accompanying images are, in order of appearance, Harry Anderson, Hugh Bolton Jones, and Frederick Mulhaupt.