"This pain, this nightmare" I'm sure when Whedon was writing it he thought it was lyrical and beautiful dialogue, as opposed to stilted and very unreal when spoken. Whoever told Whedon he could write obviously led him astray.
What happened with imo AR is that despite the lighter and almost parody tone, it lost ALL of the seriousness of the first 3 films with the exception of a few moments here or there. I couldn't and didn't believe that what any of the characters were experiencing was real.
Why ALIEN is a masterpiece for me is, in large part due to how believable each moment was; Lamberts emotional breakdown, Parkers freak out, and ultimately Ripleys default heroism that came off as if she was terrified and pissed off all at once. The characters of ALIEN are what made that movie, not the designs and certainly not the alien creature (to a certain extent).
I miss actors really acting, and selling how scared they might be in a given situation. There was a moment in ALIEN where Ripley runs into the creature in the corridor. She gets so scared she seems like she is going to throw up. THAT is fear. That is what these films have been missing...authentic fear married to authentic characters.
For all of ALIENS greatness, it did not carry this sense of realism over, nor did the masterpiece that I believe ALIEN3 is.