I had high hopes for this film when it was released; the main trailer that came out just before, made it look just like the kind of tense psychological horror I was hoping for. Unfortunately it was nothing of the kind. With that aside, I will say this... I have a lot of respect for what Ridley Scott was attempting to do with the movie and the idea behind it, I just don't think the script was good enough -- and the editing wasn't to my personal liking either.
I equate it more with a mystical adventure sci-fi with hints of horror; where as it should have been more of an experience containing a hapless crew who find themselves trapped and picked off by an advanced species capable of extreme aggression, that attacks them with a biological/genetic knowledge capable of subjecting them to grotesque deformations (we saw a little hint of this with the black goo -- but it should have been done better and been more prominent). This, in my mind, could have made it worthy of the body-horror genre that was set up in 'Alien'; all the while, leading to the introduction (internal chronology-wise) of the classic alien beast.
all in all, he tried, but he dropped the ball.