As a native Chinese speaker, I don't quite identify the genre of his work as "martial arts", it just should be "Wu Xia", which can not be translated flawlessly into English, like "Zen" or "Tao".
I consider wu xia as fantasy with martial arts, as much as western stories have any resemblance to what really happened in the "wild" west. I think Jin Yong's draw, as with most fiction writers, is placing the fantasy within a context of current social issues, thus allowing readers strong identification.