Feudalism feels more like Gryffindor to me. It was more about personal authority than about cunning. Not to mention he was the one with the sword.
There's also the power behind the throne. Cardinal Richelieu was definitely a Slytherin. (Well, the character in Dumas was; I don't know so much about the real person.)
How about the Vedic castes of India? Brāhmaṇa = Ravenclaw, Kṣatriya = Gryffindor, Vaiśya (later Śūdra) = Hufflepuff. Nobody admits to being a Slytherin, which is suspicious, don't you think?
Update: This post has also been superseded - new comments belong in the latest thread.
The second thread has now also exceeded 500 comments, so after 42 chapters of MoR it's time for a new thread.
From the first thread: