As much as I love Aliens, no, it does NOT have one of the best scripts or dialogue ever. Its great for the kind of film it is, but it is no where near as brilliant as anything by Billy Wilder or Ingmar Bergman. Two people I can tell you've never even heard of.
I don't think the dialogue or script in this game is that bad. I found the dialogue generally okay. My main problem is the way Cruz talks, particularly that motivational speech when you return to Hadley's Hope after saving the marine captive. Its typical military movie cliche dialogue. Not bad, but not great either.
The ONLY reason you hold Aliens in such high regard is because it was the first to do these things. Had James Cameron's script been filmed these days, everyone would be ragging on the writing.
Issue with the dialogue was more the lack of it than anything. The lines are decent enough, but the character interaction in the game is too minimal, largely because the number of characters is minimal. Most of the game is just O'Neil by your side with Winter fluctuating between mute and talkative.