Gryffindor: Bravery, chivalry
Also boastfulness, pigheadedness
Ravenclaw: "Book smarts", a thirst for knowledge for its own sake
Slytherin: Ambition, cunning,
Also thuggery and contentment being a lackey as long as it gets you what you want
Huflepuff: The rest
A few examples to start off with....
Caius: Gryffindor. Proof that a Gryffindor can be evil. Devoted to his charge to the extent it would destroy the universe.
Ravenclaw: ???
Rinoa: Hufflepuff. Gentle, dedicated to helping others and very empathetic
Slytherin: Most villains but for a good Slytherin, how about Shadow or Amarant?