The "best" dog food depends on the particular dog. I have three different dogs on three different kibbles... Bulldogs are notorious for food sensitivities. My allergy dog does best on the kibbles in the Acana Singles line. They are grain, potato, and chicken free. There are three proteins to choose from: duck, lamb, and pork. I rotate them with each bag, since the available proteins aren't this dog's problems.
My old man boxer does well on Fromm Gold Adult, which is a moderately priced food, and is grain inclusive. He might do well on the Acana Singles line kibbles too, but I can't afford them for him. Fromm also makes some very fine grain free kibbles (about the same price point as Acana).
My new foster, Hallie, is eating Nature's Recipe Grain Free, which isn't my choice, but it's what the rescue supplied me with, and she's doing fine on it.