When our oldest was 2, we took a road trip (with my mom). All my DD would eat was French fries and milk. My mom was constantly lecturing me "you've got to make her eat!". Since she was pretty picky on her food ever since we started her on solids, I had already had a talk with her pediatrician. He said she was in perfect health, not unhappy, and just let her eat what she wants. He said it's possibile to set up big food issues if we focused on making her eat all the "right" foods. She's grown and out of the house now, and eats whatever she wants, is still healthy and happy.
Our youngest DS was similar. Only corn dogs and mac & cheese. Until I started having him help me make dinner. Then he would at least try a bite of different stuff once in a while. But still, basically, corn dogs and mac & cheese were his go-to food.
He's in college now, and bigger than I am. And healthy.