I have a 4 year old weimy and I want to know the best food for him?

I'm currently feeding him Bill Jac (4 cups a day as suggested on bag for his weight) but I notice he doesn't really eat it the way he would eat his Ol Roy, which to me is cheap and barely healthy. Thought about feeding him Beneful or Pedigree but looking at the ingredients I'm unsure since I read about meat being the 1st 5. Suggestions?