Well, it all depends on your cats diet. What did your cat start with? Cats, unlike humans, would rather eat the same kind of food all of the time than mixing it up.
Do you change your cat food often? If so, it may be the problem.
Did he just start becoming picky? It may be a problem with his digestion. Buy him fresh cat-nip. Not only will he love it, but cats eat it in the wild to help with digestion and tummy aches.
Wet food is generally better for a cat than dry food, although dry food is easier to store and doesn't go bad quickly.
Wet food also contains a lot less fillers and carbs, and keeps kitty hydrated.
Hope this helps and good luck!
hope this helps.