C.P.
I know exactly this O.. My daughter (8-yr) is the same way. Only O. thing she is never tired of is milk and cookies (only oreo) any time. I guess it might be the age, so for now I don't force her for anything, when she gets hungry, she has to eat (no other option). She does not even like her favorite dishes that I used to cook for her. Its frustrating. Try to keep it simple and basic diet that they need for healthy growth. Don't worry about feeding him a variety of things. If he says he's done with O. thing, don't even give him for few days or week, and then O. day try to eat in front of him he may ask for it again. But again that' my experience with my daughter.
As long he eats something healthy, don't worry too much.