Best: Indian, Nepalese, Thai, Mexican... I like it hot. But also Italian for those days when I don't like it hot.
Worst: Irish, which is pretty much the same as English. They're taking a bit too much flak in this thread though, because it's not THAT bad. It just seemed that it's mostly stews, which I don't really care for. And this excludes the breakfast, because that's awesome (although somewhat artery-clogging ).
I also don't like Japanese, but as I've only tried sushi and that only once, I don't really have a good ground to judge them.