The problem with a lot of supermarket foods is that they are mostly filler. (corn and corn meal) So you have to feed more, they poop more, and generally they don't have the best quality ingredients. There are some varieties that are better than others. Usually the first 5-7 ingredients can give you a good idea of the quality. If corn is the first ingredient move on.

I won't discount supermarket foods entirely as I've heard too many breeders and performance dog owners say they feed a supermarket variety food and their dogs look great. Mine don't do as well on them. Their coats get dull and they shed a lot more. So I stick with my Canidae as much as it pains me to pay $35 a bag!