I've just rewatched Aliens (so you don't have to), and bloody hell, it's like Grim... has never watched it. The beginning bit where the marines storm the reactor area with the "goddamned town meeting", all of the marines who go missing other than Apone and one other whose name escapes me are expressly shown/explained as being dead - so other than the two or three blown up by the ammo explosion, the aliens killed them. Similarly, there are then several people who die after you sees the alien tongue thing come out of its head (including the female dropship pilot, and Burke). Seriously Grim,..., have you actually watched this film?

Apone: Attacked by an Alien, but not killed.

Bishop: Ripped in half by the Queen - which would obviously have killed a human. Wasn't trying to bring back hosts for implantation though, so doesn't count

Burke: Not killed by the Alien - note that no-one discovers his body when they break through the door he locked - so dragged off. (a deleted scene exists which shows he survives and is cocooned)

Crowe: Killed by ammunition bag exploding.

Dietrich: First one to be attacked, dragged up off the floor. Dragged off to the nest. "The Sarge and Dietrich ain't dead, man! Their signs are real low, but they ain't dead!"

Drake: Killed by acid spray caused by Vasquez(?) shooting an Alien stood next to him.

Ferro: Most likely attacked by the Alien with a view to being dragged back to the nest, but the Alien won't be smart enough to realise that disabling her would crash the ship and thus kill them both.

Frost: Killed by Dietrich's accidental flamethrower discharge before falling over a railing.

Gorman: See Vasquez.

Hicks: Survives.

Hudson: Dragged under the floor by an Alien, fate unknown. Most certainly dragged off to nest. (apparently Aliens: Colonial Marines confirms this during the game)

Spunkmeyer: Fate unknown, but probably disabled by the Alien, but not killed. Note that there is no blood or anything on the Alien's mouth when it hisses at Ferro moments later.

Vasquez: Kills herself and Gorman with a grenade to avoid being carried off to the nest.

Wierzbowski: Fate unknown, but his screams seem to echo "around" a corner which suggests he's been dragged off rather than killed.

And as Hudson notes, the only two missing marines who are showing vital signs are the sarge and Dietrich.

those monitors that are all visible from where they were standing, and all have very obvious vital signs squiggles on them that sort of you know jump out as being flat or not flat?