What is the best mass market brand of cat food?

I live in a remote area of Canada, and the only types of cat food that are available locally are the mass market supermarket brands (Whiskas, Purina, Purina ONE, Iams, etc.). The only available premium type brand is Science Diet. I know that a lot of people recommend the all natural brands like Nutro, Innova, etc, and that in the US, these brands are typically similar in price to Purina ONE or Iams. However, the cost of purchasing these in Canada as well as shipping them to my location makes anything not available locally cost prohibitive. Of the major brands, which are the best for my cats? Looking at ingredient lists alone, Iams appears to heavily by product and corn meal laden. Purina One appears to be somewhat better than Science Diet. Any suggestions?