In the best fu movie tradition, Mercury Man's plot basically makes no sense. We get an explanation of the hero's super powers that totally fails to address the other superdude running around, a conflicting Engrished technobabble explanation that actually removed information from my mind, and then finally it takes the bad guys the entire movie to think of the most practical use for their magic amulet.
But who needs plot when you have
However, MM is no Peter Parker. For one thing, he is completely irrelevant to the climax of the movie. If you're getting shown up by the comic relief character, you got some problems with your heroing, though this may have been foreshadowed when the elephants kung-fu double-teamed him.
Another sign that he may not be a very good hero is that he will straight up murder people. I'm not sure this is intentional, either on his part or the filmmakers', but as depicted, no one could survive the mangling he hands out to getaway cars, and we don't see anybody get out either.
So what I'm saying is, this movie isn't "good" by conventional human standards, but it's certainly watchable. If for nothing more than a cadre of Engrish-spouting villains and transsexual fashion designer "big sister" kung fu battle against frosted-hair mad scientist.