Despite the name the rankings are relatively arbitrary. I just wanted to fool you. The only actually definitive ranking is this, the top tier family guy funny moment.
Carter Pewterschmidt - Walk Like An Egyptian
I feel like I don't really have to explain why this is the funniest moment, but I will. Carter is an extremely underutilized character. Most of the time he just serves as a boogeyman for Peter, but you get clips like this where they let him exist outside of his adversarial relationship.
Surely you also see why the song choice is funny? This was well before Family Guy stepped into the fray of JoJokes! Even a simpleton like your average MFGG poster could see the comedy!