The combination of "good" and "Martial Art" films is generally the contradiction here. However, if you are looking for films that pertain to Korean Martial Art (specifically Taekwondo), you could look for ones done by Grandmaster Y.K. Kim. He is a movie producer in Korea, with his own production company. He is in most of the Martial Art Magazines advertising his business seminars. I had the opportunity to attend one of his seminars once, and be his partner in a demonstration. He made a movie called "Miami Connection." Again, its not great, but he does Taekwondo.
I'll look further and see if I can come up with more (I know I've seen others, I just don't recall them off-hand.)
CM D.J. Eisenhart