M.F.
Don't worry! He'll eat when he's hungry.
It's great that you offer him what the rest of the family is eating. Don't get into the habit of making him something different now. You'll become a short order cook in no time.
All kids do this, and they will quickly learn to control the menu and mealtimes if you give in and start offering cheese pizza and goldfish because you think "that's all he'll eat," and if you start pulling out snacks 30 min or an hour after you've offered a meal (which he didn't touch).
15 month olds are brilliant. They are completely aware of cause and effect. He'll learn in no time that if he pitches a fit about a plate of food, you'll eventually bring out something different, and something different still, etc., etc. At this point you'd no longer be his mother, but his waitress, or maybe his food slave. Don't do that! :-)
Offer 3 meals and a couple of snacks and he should have plenty of opportunity to get what he needs. Sure, he may skip a meal here and there (even two in a row!), but he won't starve himself.
And try not to prolong mealtimes hoping that he'll eventually eat. If it's been 15 min and he hasn't touched anything, consider him not hungry and pick up the food and move on to what's next in your day.
He may protest when you take his plate away, but it's not because he's suddenly hungry. It's the same response you'd get if you took a toy away -- he's just mad because you took something that was his.
Just stay focused and know that you are offering grat nutritious meals and one day he will eat them. You're in for this kind of food war for the next two years, so just stay consistent.
It really pays off! I sent my 4 yr old down the cereal isle this spring to pick any cereal she wanted for her "fun Friday" cereal (it's the one day a week I allow "junk" and sugary foods). I fully expected pink Barbie Princess cereal....but she came back with "Autumn Wheat" organic whole grain wheat squares... "like Daddy's cereal" she said. I swear I did the Happy Dance all the way through Walmart after that. Since then I've seen her make other healthy choices like "the bread with the oats on it" and trying new fruits and vegetables. And we haven't had pink princess cereal ever again!