I hate those ads too, I've been known to shout at the tv. I have one kid who will eat anything, and another who is somewhat picky. We have a 3 bite rule and the option of a pb&j or fruit. The sandwich option is not always available, it sort of depends on what we are having for dinner. There are a few things my younger son will not eat, so he gets to make himself a sandwich. These are usually spicy foods, or ones he has textural issues with. If he has enjoyed something in the past, he has to eat it when it is served. No opting out if you just don't feel like eating that.
I think kids should made to try things, but not absolutely forced to eat things they don't like. Adults are allowed to choose what they eat, and kids should learn to choose too. In my house, if you serve yourself something, you must finish it. This encourages the kids to think about what they are eating. There are some foods my kids like, but I hate, so occasionally, they get the "mom hates" meals. Kids taste buds are more sensitive than adults, and they tend to have more issues with food; but you can still feed them without making a different meal for everyone. There are also some foods my kids will never be served, because I won't fix food that I won't eat, and I won't eat liver, tripe, kidneys, brussels sprouts, asparagus, pickled herring or lutefisk. We also do a lot of fruit based "desserts" because they up the number of servings my kids get, without them thinking about it. Crustless pumpkin pie is a favorite, as are berries with yogurt "cream".
The reason I'm not of the "finish every bite, eat what I fix" school is because my parents were. I was forced to eat things that made me vomit, and when I refused to eat them I was served them for the next meal. I could out stubborn my mother every time, because even after being hungry for three meals, I still wasn't going to eat something that made me throw up. As an adult, I am very fat. I think that the "clean your plate" ethic helped get me there. I have finished many a restaurant meal that was too much food, simply because I felt I should. I'm getting away from that, but it is very hard to unlearn that behavior.