BMW has a lot to say on life and it's mostly good. The Father wasn't stupid, which was nice. He was funny, but also smart, helpful, strong and loving. The same with the Mother. She was smart, funny, loving, but she wasn't a man-hater and that was nice to see. Cory's parents were excellent parents: they loved each other, their kids; they were a family team.
BMW is a good picture of what a family can be if they are virtuous. If they encourage each other, support each other, are honest with each other, and if they have fun together; you know, loving each other. Life isn't perfect and the family and friends on BMW had problems (remember Cory getting mad at his dad on his 16th birthday? Or when Cory thought his mom didn't want him and Topanga together?), but they worked them out together without developing hate, animosity, playing victim, and all of the other junk that happens in families who give in to their vices.
Some might say the BMW family and friends are a romantic idea of a perfect family; that Jacobs and the writers are Utopian thinkers trying to get people to be something they aren't.
If television shows only give us pictures of people giving in to their passions because that is what comes "natural," of people doing their daily routine and never going "beyond" then people will never grow past giving into their passions and their daily routine. If we see people living, in what we would call extreme I guess, then that rattles the ol' mind to live differently, to live virtuously, and to do things we ordinarily wouldn't do like not giving in to our passions and doing what is comfortable. BMW is arguably a picture of Aristotelian morality: strive to live like these people or even better than these people. In my opinion, BMW creators didn't want to tell you abstractly how to live by giving you commandments, instead they showed you through drama what love between family and friends looks like.
Honorable Mentions: Full House and Family Matters