My rule always was that the kids eat what's put in front of them on their plates. Sometimes they didn't like what was there, but they ate it because it's good food for them. They were this way even if they were at a friend's house. They grew up thinking it's inpolite to tell the person who cooked the meal that you don't like it.
Another thing I used to do is tell a little fib and tell them that they used to love this stuff when they were younger. I'd tell them to taste it (take a good bite, not a tiny one) and most of the time, they did like it.
hot dogs, hamburgers and stuff like that aren't healthy enough to be eating all the time. I have a nephew ( my favorite nephew
) who's a really picky eater. That's all he wants to eat is hot dogs, nuggets and fries. when he's at my house, he'll eat what's put in front of him no problem. if his mom tries to get him to eat the same food i fed him, he refuses. go figure.