There are many guides and review sites to determine the best choices for your cat's diet. Some claim to be independent but are sponsored by large pet food companies. Here are three that are the most impartial with opinions we agree with the most, having done much of the same research. They are in no particular order. Please note that we personally only feed home made and wet food.
Yet Another Cat Food Guide: Thoughts on Feline Nutrition and Care is a sometimes irreverent but thorough look with recommendations. (Please do not click if a little salty language is not your style.)
Cats are carnivores with inadequate thirst instincts. Carbohydrate-heavy and dehydrated foods as staples are right out. I basically advocate for an anything-but-dry-food diet: feed home-made raw if you can, commercial raw and high-quality canned if you can’t, and don’t feed dry food unless you absolutely have to.
There is a fairly comprehensive guide at Reviews.com that is updated on an ongoing basis. They are currently reviewing over 1700 choices.
Susan Thixton puts out expert recommendations every year. Since she is 100% consumer supported and does not permit advertising to influence the site, the list costs $10 - and is well worth it. And there is a lot of other important information on this site that is free. Check out The Truth About Pet Food
This website, TANYA'S COMPREHENSIVE GUIDE TO FELINE CHRONIC KIDNEY DISEASE, has helpful information for cat's who already have kidney disease.