i think Edward has more of bravery and selflessness him in then anything else (whatever the reason might be, he has the capacity to leave Bella whom he loves so much) so i vote for gryffindor.
A sharp brain is one of the things one gets when changed into a vampire so nothing special about Edward being witty. moreover even with his enhanced thinking skills he is not able to make the connection between Victoria, the newborn army, and the stranger in bell's room in Eclipse until Bella points it out. So not Ravenclaw.
And he is certainly not selfish in any way at all. If he would have been then he would never have fought his nature so hard to protect the humans who were practically food for his kind. That too when it caused him pain all the time. So not Slytherin and
For hufflepuff: All of the Cullens work hard to maintain to be vegetarians but i think that its to a point where it can be called bravery instead. (Resisting that painful thirst round the clock.)
So Gryffindor from my point of view