My dog will only eat a certain dog food?

I've been feeding him Bil-Jac and researched, and found out it was bad. But he loves it. I've tried to switch to better brands like Blue Buffalo and Solid Gold. But he won't eat either! My mom is convinced by the vet, that we should feed him anything he eats. But I don't want it to be unhealthy. When I try to feed him it, he wont eat. Its really making me mad. Help??