Anyone hoping for another "Alien" will probably be left disappointed. Although it's set in the same universe and has ties to the original; with the infamous "Space Jockey," it isn't of the same sci-fi/horror genre that Alien is.
It didn't live up to its hype (but then again it probably never could) but its a good sci-fi movie, though the pace does meander in places. As many have already said the script is poor as is the characterisation. Most people will probably love it, it ticks all the right boxes for a summer blockbuster. I preferred Alien.
I thought the part about Elizabeth getting the alien out of her was not necessary....it didn't add anything and wasn't realistic to think someone who just had a C-section could run move around so well, even after given all the pain meds she was on.
I like the ties to the first Alien, it explained what needed to be explained about the origin and 'why' of the space jockey. The gray matter was of their own engineering & backfired on them, simple as that.
I don't understand why they (the space jockey aliens) would want to destroy us, however, and be violent and kill. That part is unanswered, as it was to the main character.
A sequel will need to follow to tie up loose ends.