Unfortunately, this film neither features real martial arts, nor is it a classic. It hardly even features Bruce Lee, except for some old footage that has been re-dubbed to make it look like Lee actually agreed to this film being made. I hope somebody got sued for this one.
This could have been a good documentary about the "1979 Karate Championship" but most of the footage from the karate matches is obviously staged, and has little to do with Chinese martial arts. Some interesting "facts" were revealed by this film however. For instance, prior to watching "Fist of Fear", I had no idea that Lee's great grandfather was the greatest Chinese samurai warrior.
There are a few funny moments in the film (the Bill Louie Kato scene, or when Fred Williamson is introduced for example) but if you have any respect for Bruce Lee or film-making in general, I would highly recommend avoiding this film.