L.E.
I have the same problem with my 22 month old son. He lives on pretzels, goldfish, yogurt, waffles, french fries, grilled cheese sandwiches, pizza, strawberries and grapes. Occasionally I can get him to eat a turkey hotdog or some mac and cheese. He will rarely try anything else. No pasta, no fresh, frozen or canned veggies, no meat. He won't even eat cake or ice cream! Very frustrating.
Here is what I do: I "smuggle" healty food into the foods he will eat. I mix jarred baby food carrots in his mac and cheese. Also I mash the yolk of a hardboiled egg into his yogurt. Sometimes I can sneak a slice of ham in his grilled cheese or put small pieces of broccoli into his pizza.
Jerry Seinfeld's wife has written a book on how to hide veggies in your child's food so he doesn't even know he is eating them. She suggests pureeing the veggies yourself but I just use jarred baby food.
I also discovered that my son needs to be distracted. I put bug stickers on the ceiling, wear funny hats, give him toys and sing songs to distract him. Sometimes I don't even think he knows he's eating. It's exhausting for me, but at least he's eating!!
Get creative! Good luck!