Starfleet-Houses » Q: The omnipotent pest that has tormented Picard, Sisko and Janeway alike, Q is a definite shoo-in for Slytherin. He’s cunning, clever, thinks he’s incredibly hilarious, has little care for the trivial cares and feelings of species below him, lives entirely by his own set of rules and bows to no one else, is very independent, and causes havoc wherever he steps. He sees people as little playthings and unworthy of his real attention. He has a few bonds - but is incredibly selective about them, and still then refuses to admit his closeness to these people. Even in the Q continuum, he is the renegade and the rule breaker, the irrepressible Q.
Starfleet-Houses » Captain Jean-Luc Picard: A deeply intelligent man and a fearless leader, Picard is bold, courageous, authoritative, and has a very strong sense of morality and justice. He trusts his own judgements in drawing the lines between right and wrong, and perserveres through many hardships while remaining a well-respected and well-liked leader. Fiercely independent and stalwart, Picard is an exemplary member of Gryffindor House.
Now see Picard I would have put in Ravenclaw… But both Sisko and Picard are really Ravendors/Gryffinclaws.