I think the main problem of sorting CCS characters into houses is that it depends on overall personality verses short span personality.
Example: In the beginning of CCS Syaoran would be more Slytherin house. However as the series progresses, it's clear he's more a Gryffindor. Thus why it's hard to choose. o_____o'''''''
So here are my preferences:
Sakura I'd probably place in HuffPuff.
Tomoyo, I'd place in Ravenclaw (very creative, and quirky)
Eriol I'd place in Ravenclaw (very intelligent/ do what is wise)
Syaoran, is as closer to slytherin than any of the others, sooooo he gets placed there. He'll be a good slytherin tho.
Kero(gryff)/Yue (Ravenclaw)/Mizuki(Huffpuff)/Spinel (Slytherin) would probably be teachers for the houses.
Clow Reed would be headmaster. Definately a dumbledore type.
Naoko: Ravenclaw. Hands down. Crazy writer.
Risa: Huffpuff. Such a sweetie
Takeshi: Gryffindor. He should be in Ravenclaw, but stupidity in telling lies is strong with this one.....
Yuki (seperate from yue): Huffpuff