Personally, if I see coloring or by-product, I don't feed, so I don't buy grocery store food. But I know Sheeba has the chicken only range, with no by-product, its shredded chicken. Anyway, grocery or none grocery, so long as your kitty is willing to eat some wet, I suppose it is still better than dry in most ways, at least your kitty is kept hydrated and not starved to death, lol.
ET would rather starve than to eat food that he simply hated - some of those highly recommended foods is what he hated (sigh...what to do). Thank goodness, there are still some other good brands that he will still eat. So, the point is, whatever food, so long as kitty is willing to eat.
Ok, I am copying some of the links laurief posted