10 years ago
I don't know, I like when they're standing upright. Not specifically in this movie (though I like the idea of seeing Resurrection's Xenos as demons; freaks even among their own kind) either, because the one in the first Alien film would stand on two legs while slowly creeping up on someone. This was (and is) incredibly horrifying because it would do this even when the person clearly saw it coming, meaning it knew its prey couldn't do anything to stop it.
I'm specifically thinking of the scene where it basically fondles and rapes Lambert, albeit (sort of) off-screen.
Come to think of it, I think the scariest scenes in the movies involve the Xeno standing only on its legs, such as the scene when a Warrior kidnaps Newt or when the Giger Drone kills Lambert. Coincidentally, the only time they're ever quadruped is when they're in groups getting murdered by things that violently explode/shoot at them (Scar's plasma caster, mini-guns, the entire goddamn Sulaco...) and it makes them seem pathetic, honestly.
The only exception to this is the Dogalien (To be fair, though, no one had a gun or an exploding ship) and probably Grid - I don't remember how he dies on-screen, if at all.