Lois would totally pwn Marge; she knows kung-fu.

Stewie could completely blow Maggie apart: sue Maggie tried to kill Mr Burns, but that was a complete fluke. Stewie has the brains; he can even talk already, and is a mastermind to world domination!

Peter and Homer: I think Peter would win. He is much cooler!

Chris would simply flatten Bart.

Brian talks, and once wrote for the New Yorker (almost ) Santa's Little Helper learns fast and fathered 23 puppies, but at the end of the day, he's still a dumb dog. Brian's drink problem counts against him, but what he lacks in sobriety he more than makes up for in smarts.

Lisa does have the edge over Meg; Meg is just an average teenage girl; Lisa is unnaturally smart, and concerned about the environment.

Snowball II vs. the psychotic kitty the Griffins had in the Brian: Portrait of a Dog episode: No contest.

Final result: Simpsons 1, Griffins 6 (including the mad cat's win)

P.S: I wonder what Flanders would make of Quagmire... O_o