There was a point in our growing up that if we complained about dinner we had to cook the next meal for the family. We learned pretty early in the game to just smile sweetly and thank whichever parent had prepared dinner!
I don't have kids so technically I shouldn't get to vote here (my DOGS will eat anything ), but I have a very wise sister.
Her approach is to let her preschoolers pick three foods that they don't have to eat. Any three foods. Other than those three choices, they must eat everything placed...