We have to remember Peter Pettigrew was sorted into Gryffindor as well.
I actually do think Han Solo would be in Gryffindor. I don't think he's as sly, cunning or subtle enough for Slytherin. He has kind of a Sirius Black-type Gryffindor thing going on. Han's kind of reckless, when he can't turn a conversation he just shoots...first. So I can definitely see an argument for him for being sorted in Gryffindor.