I rotate food, reason being is that I want to be able to at any time switch foods without having to worry about tummy upset. So I use a base food all the time of Fromm's Surf and Turf… one small bag mixed with a variety of other high quality mostly grain free dry... I have used Taste of the Wild, Natural Balance Potatoe and xxxx, Evo (although not so much since they were bought out) Blue Buffalo, etc.... I mix with wet, again a variety of quality wet meat based. Also use freeze dried, raw, etc mixed in on different days.
I really believe that changing things up keeps them interested (however that said they have always eaten like little piggies).....