I believe the sorting hat (and the sorting quiz) has to take into account that about a quarter of all students need to be sorted into each house. That may explain why you were able to fit into Hufflepuff one year but not this year; there were simply too many Hufflepuffs this year.
And don't worry, just because every evil wizard is a Slytherin doesn't mean every Slytherin is an evil wizard. ;-)
Oh, I am very happy to be in Slytherin. I wouldn't have it any other way. My whole post was about me coming to terms with and loving my Slytherin-self. :) Thank you for the comment!