Where to begin? The answer is everything.
I didn't care about any of the characters. They were boring and underdeveloped. There were just too many characters and the time wasn't utilized well enough to make them interesting to me. I suppose David was an alright character, but all the interesting questions about his character are never really answered. Like, what are his motivations? His character is kind of all of the place, and it's obvious he has some kind of agenda, but they never really delve into that. I wouldn't mind if they were subtle or ambiguous about it, but they really just don't address it enough. Also, they initially establish him as an android (although in a bit of a silly way), but they don't really explain well enough why everyone assumes he has no feelings or ulterior motives. And then they try to raise the question of whether he might actually have some feelings. But I don't feel like his lack of feeling was established well enough to make that an interesting question. On the surface, it's like they wanted to ask the kind of big questions about David that were asked in something like Blade Runner, but the problem is Blade Runner does an amazing job with those ideas, whereas Prometheus has no idea what to do with them.
As for the other characters, Charlize Theron's character was a stone cold bitch the whole movie. It's almost like there could have been an interesting subplot to her character, but there were just too many other characters that the movie couldn't donate the time to actually developing her. Also, I laughed out loud when she said the word "father". That scene seemed like it could have been far more significant if the movie was executed better. Oh and Weyland looked hilarious. I don't understand why they didn't just use an old man for the part instead of using an old man mask that made me laugh every time I looked at it.
Glasses guy and punk-rock geologist seemed like they could have been more interesting if they weren't so underdeveloped before being killed off. Also it didn't make sense how they were all scared and running away and then glasses guy suddenly wants to go up all close to snake penis monster.
The captain was kinda cool, but he didn't get much screen time or any major scenes, except maybe the suicide attack, although that scene had the two pilot characters which literally had nothing to define them other than their little bet.
Oh yeah, and I guess that one woman sort of became the main character near the end of the movie. The c-section bit with her was entertaining, but other than that, she was totally boring. She was certainly no Ellen Ripley if that's what they were going for. Oh yeah, and I guess her husband was a character too. The scene where Charlize Theron set him on fire might have been good if I actually cared about him.
Enough about the characters though because I think it's pretty clear by now that I was not a fan of them. But maybe the plot was at least good? No. There was nothing even remotely entertaining about the overall plot to me. They set the movie up with these big important sci-fi questions about the origin of human life and why the "engineers" created us, but none of that is ever even kinda answered. Not even a sliver. What we got instead when they finally met a living engineer was a big human-looking thing that just tried to kill everyone without any kind of given reason. That was one of the least rewarding build-ups ever. Oh but wait, maybe if we're lucky we'll get our answers in Prometheuses! Oh boy!
Oh and if the birth of the alien from the engineer's corpse at the end was supposed to answer how the aliens from the Alien series came to exist, that's a pretty unsatisfying answer to a question that never really needed an answer.
Prometheus is a movie that wants to be "big and important", but in the end it never aspires to anything. Sure, it looks "important", and it aims in the right direction, but it just can't keep up with its own ideas. And it's not even entertaining in it's failure to do that.