This film is OBVIOUSLY not meant to be taken seriously. It is very clearly intentionally a "joke" of a film. That people would complain about bad acting, strange dubbing, and/or a convoluted plot just leaves me flabbergasted.
From the very beginning, it should be evident that a big part of the point of the film is its own self-deprecating humor. Jackie loses his memory and is picked up by a primitive African tribe. The chief asks him, in an unintelligible language, "Where do you come from? What is your name?" to which Jackie replies (not understanding the questions) "What am I doing here? Who am I?" This is a JOKE, folks.
A few minutes later, Jackie saves a snake-bite victim with an IV he improvises from a COCONUT! When he's returned to "civilization," the doctor is impressed with that tactic, saying, "That coconut IV technique is only used by elite military units!" Is there any way to even dream of taking the plot/dialogue seriously at this point?
The acting is "bad" by design. The actors were obviously told to ham up everything they did. The meeting of the American intelligence officials is a completely ironic reference to the same sort of scene you'd expect in any James Bond movie. Dialogue is intentionally absurd, plot developments are intentionally obvious. The "Morgan" character is played perfectly (and hilariously) as a crooked CIA operative out for his own gain while feigning loyalty to the USA.
Yuki is a master stunt-driver with the naivete and wide-eyed innocence of a schoolgirl. Christine Stark is a completely laughable "reporter" who fools Jackie only as a result of his head injury; after she's "exposed," she rescues Jackie in an golf cart that can't seem to move faster than an electric wheelchair.
That the villains actually join each other in a verse of song ("Friendship, friendship!") near the end should serve as a good reminder of just how camp this picture strives to be. To criticize it for this as a "failing" seems to me to profoundly miss the point. Did the same viewers dislike that "Hot Shots: Part Deux" was absurd too?
Overall, the strengths of the film deserve the attention: it is a very funny parody of the overplotted "action/intrigue" genre, it has a terrific car chase, notable action sequences, and a terrific Jackie-Chan-Style fight scene at the beginning of the film's climax.
Perhaps I enjoyed this movie because I had grown up watching the "GI Joe" cartoon series, and had always been rather insulted by the fact that it managed to be both preachy and stupid at the same time. If you're looking for a great 100 minutes of parody and HUMOR, I'd recommend this movie. If you're more interested in believability and suspending your disbelief, this film will definitely not work for you at all. Inappropriate expectations would be the only "problem" I can imagine that would reduce one's enjoyment of this film.
If you want a more serious Jackie Chan film, you might try Drunken Master II, or Police Story. But if you're looking for an enjoyable and sardonic 100 minutes, this is truly one of Jackie's great vehicles.