Why do so many like to quote Nietzsche so much?

I don't get it. What's the attraction? Why is he so popular? To me he comes across as an old, grumpy curmudgeon who'd be the type of person who'd get a thrill from telling little children that Father Christmas isn't real. Or the main character from the TV show 'House MD', played by Hugh Laurie. The kind of person that no one would ever want to be around.