According to the language consultant of Prometheus Dr. Anil Biltoo (who also appears in the film) the dialog that David learns and speaks to the Engineer is actually Proto-Indo-European and was:
/ida hmanəm aɪ kja namṛtuh zdɛ:taha/…/ghʷɪvah-pjorn-ɪttham sas da:tṛ kredah/
Which roughly translates to:
This man is here because he does not want to die. He believes you can give him more life.
So he really does say what he was expected to, apparently there was more to the conversation that was cut but might be put back in for the Director's Cut which I'm looking forward to.
So is that disappointing? Or are you just happy to have it confirmed?
Source: The Bioscopist