royal canin is not great, one of the better mainstream foods, but it's expensive. it definitely beats the heck out of purina, science diet, nutro and so on, but doesn't measure up to innova, canidae, eagle pack etc.
you can get much better quality brands for the same price as you'd pay for royal canin.
the drawback is that you most likely won't find the really good brands at the big chain stores like petco or petsmart. i know petco is doing a little better these days, they sell eagle pack through their website and in some stores, and some also sell solid gold, but you are really much better off shopping at a small, local chain or individual store.
petsmart only offers one brand of food worth looking at: blue buffalo. it's quite expensive tho, you can get most other high-end brands for less.
if you want to support the san diego SPCA, they sell natura foods at their 5500 gaines street location. (619) 243-3451.