I love the whole Alien-franchise (AvP doesn't count; more on that further down the post), but what I don't get is why people call Aliens a horror movie. In truth, it's actually a war-movie. Just watch it again, but imagine the aliens are nazis/vietcong/communists/whatever and pretend it takes place on Earth, and it's clear as day. Plus, Newt kinda spoils it. "They mostly come out at night. Mostly." Why would she say that when there are no sun, meaning no day? Or for that matter, night? Well, if you were in a real war against superior enemies, when would you prefer to strike? In broad daylight or hidden by the dark of night? Exactly. You'd strike at night. They would never know what hit them.
As for AvP, I don't consider that part of the Alien or Predator universes at all, but count it as a third franchise. While I enjoyed Predators, I see the Predators as hunters, not killers. Why then would they start killing off the aliens as a hobby? And as for the aliens, since when are they braindead cannon fodder? They are actually very intelligent. If they had been as braindead as AvP wants them to be, how do you explain the lone alien not going on a killing spree in Alien? Why do the aliens hide in Alien 3 instead of going on a rampage? It's because they know they are outnumbered and would be in danger if they attack head on. Attacking from the shadows is a much better option, as it would let them pick off the enemies one by one and be safer. Just like any other intelligent creature. Plus, in Aliens, the aliens captured the humans so they could be used for breeding. Mindless aliens would just kill them and be done with it.