All of the above food suggestions are good.
My cats are 6 1/2 years old.
I have been using Nutro Complete Care Wt. Management dry /pouches with an equal amount of Nutro CC Senior pouches.
I also give them Meow Mix Pouches 1/2 shared a couple time a week as a treat.
I add a teaspoon of filter water to their wet, which they have AM/PM.
A quality wet food, because of it's water content, is very important.
It helps keep your kitty well hydrated, which is essential to long term heath.
I have tried to rotate their diet without much success...
their tummy's become upset even though I go very slowly.
How old is your kitty?