Actually Peter Griffin doesn't really save the day, and isn't too good-natured.
Atleast he displays some flicker of intelligence unlike Homer.
The kids aren't really wacko...Chris is just really stupid, but isn't a torublemaker (unlike Bart). And Meg is just a typical teenage girl who can't pull any boys and who always hassles her parents for plastic surgey. She isn't super intelligent (unlike Lisa). And i think Stewie speaks for himself...The british accent goes wonderfully with his villainous character.
And i do know that Family Guy owes alot to the Simpsons, but the difference is that Family Guy is intended to be funny and to entertain. The simpsons simply has repetetive and predictable storylines, and even worse funnies (Family Guy has hilarious character or flashbacks around every corner) I think its supposed to teach us the values of life or something like that, because every episode always ends with a OMG-so-cheezy feeling of happiness.