So we got Andy and Bob. They are both digital artists, they both have great skill and knowledge within digital painting. Andy, he likes to do photostudies, so he paints one, using this one photo of a car as a reference. He spends countless hours rendering it, making it as correct, similar and realistic in comparison to the reference photo. At first glance, you wouldn't be able to say that its a painting.
Now Bob, he is an innovative person, he likes to paint from his mind. He doesn't have a lot of time on his hands, but plenty to get a good result from the time spent. He paints lets say, a character he came up with who is striking some sort of pose in an environment he also came up with from his mind, something that nobody has seen before. His work is all anatomically correct, the perspective is correct, on similar factors its flawless. Only thing that differs is that he didn't put much time into rendering the piece all too much, the brushstrokes are visible. Its not bad at all, just clearly a painting, as he didn't even have half that Andy did.
Now, irregardless of that Andy spent a whole load more time then Bob did, he still lacks the innovation, charm and "imaginative-ness" which Bob has. His work is all polished and pretty, but it has no feeling, no emotion nor anything thats actually >interesting<. We've all seen that photo of the car before, but we haven't seen this character and environment which Bob painted up until now, which is new, fresh and interesting to look at.
Andys work can solely be valued in effort and time spent, whilst Bob has an actually artistic value to his.