FF Characters in Hogwarts Houses

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?

Ignis for Ravenclaw!

Also, Ravenclaw is much more than about book smarts. Hufflepuff is the house of learning and hard work - Ravenclaw is about cleverness, individuality, creativity, thinking outside the box, etc.

Gryffindor: Zidane, Cecil, Vincent, Zidane, Steiner, Freya, Eiko, Auron, Kimahri
Slytherin: Auron, Lulu, Kian, Cloud, Yuffie, Cait Sith, Cid (FFVII), Amarant
Hufflepuff: Wakka, Rikku, Quina, Rosa, Barret, Tifa, Aeris
Ravenclaw: Garnet, Red XIII, Vivi, Yuna

Or at least, that's how I feel

I'll tackle FFVI

Gryffindor: Celes, Locke, Sabin, Relm

Ravenclaw: Strago, Setzer, Edgar

Hufflepuff: Mog, Umaro, Terra, Gogo

Slytherin: Shadow, Kefka, Bannon, Emperor Gehstahl.