Personally, if someone said "Which Hogwarts house is the worst?" I would answer "Gryffindor"
I think all the houses have bad problems.
Ravenclaw (my house): Think they are smarter then everyone else, also kind of annoying as they are "so smart"
Hufflepuff: For some of them, the kindess could be a cover. Also always taken from granted
Slytherin: Voldemort was in this house
Gryffindor: Think they are the "best" and everyones favorite because they had Harry Potter.
I think Gryffindor is just the bad house because they are boastful, self-confident, and so talented at Quidditch. I feel so bad for Slytherin. They were earning some of their respect back, after they had produced Voldemort, and then Harry Potter comes along and basically screws them.