I very much enjoy the first movie. I have watched it several times and still enjoy going back to it. I absolutely agree the plot is puddle-deep, as you said, and it makes no attempt at all to disguise its analogies ("unobtanium"), but it's mastery is not in the story itself but the way in which it is told. It's almost operatic in the amount of time it spends within each story beat. The second film failed to do a lot of the things I loved about the first one and was very forgettable.