A.L.
Hello C.!
Girlfriend I feel your pain! I have not read any of the other responses to your request, but I can tell you that I am going through the same thing---my son is 6 now and in Kindergarten. Our battle started when he was 6 months old and started solid food. He's always been EXTREMELY picky and it drives us all batty. I am a good cook and enjoy trying new foods, but our son will have none of it and like yours, won't even try it!
We've had many a stand-off at the table and finally had to make a compromise or rather an ultimatum on his part. I let him know that when he turned 6, he would be responsible for his dinner if he would not eat what I am cooking. Lets just say he's been eating a lot of cereal for dinner at night! ;)
My husband and I weren't raised to be picky so it has been so frustrating. Like your situation too, our daughter will eat anything and it just warms my heart! That being said, my son is a good boy and he's very smart. I think he'll develop his style of eating over time and I try to make whatever he will eat extra healthy: like if he loves chicken nuggets, then I make my own, healthy pancakes, mac n' cheese, etc. If your son will eat apples and yogurt---yeah! Work with what he will eat, set limits and expectations for your family that work.
It might help to talk to your doctor or pediatrician. Mine told me that my son was perfectly healthy, growing just fine, etc. and not to make food an issue. Sooner or later our children will have to learn and I'm happy that at school they are taught healthy food choices. I hope that helps and I wish you all the best!