These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Alien vs. Predator
Anticlimax Boss: Most of the bosses from the second PC game. The Exosuit is heavily armed and armored, but has an atrocious lack of armor over where the operator's head is, allowing you to bring it down with just a few headshots, or even a single bonegun round to the head; the Predator's pistol also paralyses the stupid thing with every shot. Even the Alien Queen goes down after a few bursts of minigun fire or some brief circle-strafing and whacking with the combi-stick. Predators are pretty nasty, though, especially when you fight them as the unarmed, unarmored Alien.
In the 2010 game, the queen isn't even mobile, in fact, it's less of a boss, and more of a piece of scenery you have to kill while fending off facehuggers.
The final enemy of the Alien campaign in AvP2 is Dr. Eisenberg, who really seems anticlimatic after two in-tandem Predators, seeing as you can just run up to him and eat his freaking head off.
Base Breaker: The two groups split more or less on these issues when it comes to the second movie:
Those who like the movie like it for its action scenes, increased gore, badass Predator and horror elements.
Those who hate the movie hate it for the needless gore, the poor lighting, the Aliens non-sensical behaviour and violation of pretty much everything we've ever learned about them, them getting slaughtered by a single Predator and the glee the movie seems to take in averting Infant Immortality.
Broken Base: Quite a few fans of the video games dislike the fact that the movies are set on present Earth instead of the Aliens time frame of the games and most comics.
There are plenty of people that enjoyed the first one though(and some for the second).
Most of the fans of the older PC games are already decrying the route the series has taken in the new one.
Creator's Pet: The Colonial Marines in the video games can sometimes qualify, with fans preferring to play as the Alien or the Predator. The worst case was the 2010 game, where the Marine's story was by far the longest. And then the Marines got their own game, which barely even featured the Aliens despite them being in the title.
Demonic Spiders: Facehuggers in the first two PC games are a very literal version of this trope; they kill you in one hit and are small and difficult to spot, especially in the game's dark environments. They do make a distinct scuttling noise that's supposed to alert you to their presence, though.
In the 2010 game Facehuggers are still small, fast, and annoying, but no longer kill you in one hit as your character is badass enough to automatically deflect them out of midair (although they do knock off an entire lifebar every time they jump you).
Though 2 does have a bit of Nightmare Retardant in the Marine campaign since they can have severe problems actually attaching to NPCs outside scripted events, leading to the comical sight of a bunch of Facehuggers leaping aimlessly around and bumping into people. The 2010 game's Alien campaign has similar results when you realise Six must be being followed around by some kind of Facehugger conga line.
Alien Facehuggers, Predator Stalkers, and Marine Snipers in the RTS. The first will one-hit kill the first unit they hit if it doesn't have some sort of resistance to it, the second will sap your units' health while slowing them to a crawl, and the third just shoots them so hard there's a 20 foot blood splatter opposite the point of entry.
Ensemble Darkhorse: The alien nicknamed "Grid" (because of the grid pattern on its head caused by a predator's net) has become very popular among people who have seen the 2004 AvP film because it seems to be an exceptionally intelligent and formidable alien warrior. In its very first appearance, Grid singlehandedly kills two Predators, immediately establishing itself as a badass. It also manages to dodge being blasted by a predator's shoulder-cannon, and it's seen leading other aliens into battle. Even people who didn't like the film admit that Grid was pretty damn cool.
Fan Nickname: "Grid" for the exceptionally badass xenomorph mentioned above.
Freud Was Right: Giger's rather suggestive Alien designs are in full swing.
Game Breaker: In the first PC game, the Predator's speargun was absolutely broken. It was a one-hit-kill, hitscan sniper-rifle-style weapon, which would have been remotely okay if it didn't have a fire rate of two a second, a no-reload magazine and more than its fair share of shots.
The Smartgun in the second game. The gun aimed for you, all that was left was to pull the trigger. It could even detect cloaked Predators, negating their prime advantage over the Marines. No wonder the majority of multiplayer servers disabled it.
Partially averted in the 2010 game- the Smartgun takes up both primary weapon slots and prevents the Marine from running unless they have their pistol out instead. The tracking is a bit slower and can be outmanuevered by an agile Xeno player, and only covered a certain field of view in front of the player, although it does outline cloaked Predators and hard-to-see Xenos- still less unbalanced than before, since it only shows up in exposed, easy-to-cover spots.
The 2010 game has its own problems in the form of the predator smart-disc. It's a 1 hit kill, and bypasses the melee system that was implemented by simply being unblockable. Combine that with the fact that there is no downside to using it at point blank range. Even if you miss, it will likely kill your target on the return trip if your enemy continues to fight you in melee.
In the first game the flamethrower is... well, more of a terror-breaker than a game-breaker, because once you get it facehuggers - the single most terrifying enemy in the game, due to their extremely small size, fast speed and ability to kill you instantly - become much less of a threat. Simply fire off a burst of flame at the ground and watch as the damned things start running around randomly and burning to death.
In the second game, The Sniper Rifle in multi-player games is arguably a case: No gun sway to speak of, and it's accuracy is not affected by NOT using the scope. By using a piece to tape and a marker to make a crosshair on your screen you now have a weapon that works at any range and which usually causes 1-hit-kills to any part of the body. The only limitation is restricted maximum ammo. Oh, and on servers that enforce the use of classes, the Marine Sniper also has access to a versatile grenade launcher with EMP (de-cloaks predators and stuns them; it also stuns any species it hits too.), Proximity (detonates on approach), spider (chases the target) & conventional grenades.. With a steady aim on the player's part, Marine Snipers can be highly-mobile killing machines.
Good Bad Bugs: In AVP 2, if you can get out of a Chestburster's sight area while it's emerging, it'll just drop out and sit there staring straight ahead, as if thinking "Ok, now what?"
In the RTS, it's possible (through spamming the "move" button) for Predator Hunters to fire on the move... and they have excellent range. You can kite most enemies to death this way.
Narm: In the first Aliens vs Predator game for the PC, the video messages were originally done by actual actors. The gold edition, and by extension the Classic 2000 modern re-release, replaced them with performances by the Rebellion dev team staff. Although the production values on the Rebellion vids are higher (with actual props being used), the Rebellion staff are clearly not actors, and turn in some really Narmtastic performances.
Surprisingly Improved Sequel: The second movie had a greater focus on the monster action and gore than the first, which was one of the main complaints fans had about the first. Whether this makes it better or worse, of course, is entirely subjective.
At one point in Requiem, The Predalien and several facehuggers attack a group of homeless people living in the sewers. One of these people had a dog. In Alien 3, it is revealed that a facehugger impregnating a four-legged animal, such as a dog or an ox, would produce a quadrupedal variation of the Xenomorph known as "The Runner". If one of those facehuggers attached itself to the dog instead of one of the homeless people, we could have had the chance to see two powerful Xenomorph hybrids in the same movie.
Too Cool to Live: The general opinion people have of Adele Rousseau, with most reviewers stating that she's the only character they liked. So of course she gets facehugged.