Here is what our Veterinarian told us about dog food: there are a few that are complete, balanced diets. He recommends Purina Pro Plan.
He says that the cheaper brands are mostly junk food. He has seen dogs suffering from malnutrition when they get nothing but Old Roy. Here is an example of how they do it. The nutrition from corn is all in the pulp; the skin itself has almost no nutritional value. A food manufacturer can squeeze out the pulp to make corn syrup. The remaining skin goes into the cheap dog food, which is allowed to list "corn" as an ingredient.
As for comparing dogs to wolves, they are not the same. Wolves are complete carnivores. Dogs, by living with humans, have developed the ability to digest vegetables. (Got that from a NOVA tv show.)