truthfully I think all toddlers go through phases where they have favorite foods they eat constantly.
Keep offering him bites of the food you want him to eat. He may shock you. In the mean time sneak in healthy foods whenever you can. My son went through period of time where he ate french toast for breakfast daily. Make him a pizza with whole wheat toast spread with a little pureed vegetables, then some pizza sauce. Cut up some chicken really fine and mix it in with his mashed sweet potatoes--he may not even notice it is there.
my youngest son has done his different food trends, but I think at 2.5 years old I have him on a good meal plan now. He likes the lunchables jrs with diced meat, a little cheese and small crackers. He does eat cheeseburgers a few times a week for lunch. He also likes grilled cheese, broccoli (steamed pretty soft), peas, corn, green beans, macaroni and cheese.
another sneaky trick is to give your son the food that he likes, and load your plate with stuff you like, and want him to eat. Show him how much you enjoy it. Don't offer it to him unless he acts like he really wants it. Then try to convince him that it is grown up food, and he won't like it. He just may take a bite and like it to prove you wrong. My son just started eating sliced turkey deli meat off my plate recently. He won't eat it on his plate.