Many grocery stores and places like Walmart are actually carrying some fairly decent foods these days. They still have loads of junk foods, but a few decent ones have slipped in.
That said, I don't know if you're specifying Walmart because you're looking for something cheap or because it's the only place you can get to.
If it's the only place you can get to and price isn't a huge obstacle, then I'd suggest Newman's Own. Other than that...the best of the standard Walmart/grocery type wet foods is Iams (imo). Not great, but you can certainly do worse.
Holly, Misty & their friend, Jake, the dog.
Onyx, Callie May, Maggie & Kobi forever in my heart.
Yes, I know I need a new signature pic...someday...