Gateway Series: With all its flaws, the first film introduced both the Alien and Predator franchises to the generation born in The '90s, most of them young people who only knew them as obscure horror franchises from another era of cinema. It can be said that, if the two fandoms's received any new blood through the 2000s (and thus, a huge part of the expectation for Prometheus and Predators), it is actually thanks to this saga and its spin-offs.
For the games
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.
Broken Base: Most of the fans of the older PC games are already decrying the route the series has taken in the new one.
The Primal Hunt expansion pack caused an interesting variation of these. Everyone was crying out about how "their species" got the shaft when it came to new equipment:
Alien players complained that the only addition was allowing Predaliens to headbite, restoring far more health than they were able to with claw attacks. This greatly mitigated Predaliens' "glass cannon" status.
Marine players complained that all they got were dual pistols and a 360-degree motion tracker. Dual pistols with AP rounds could be devastating against armored enemies, and the 360-degree motion tracker made it much harder for aliens and cloaked predators to sneak up on them (though these were only available to "Corporate" Marine players).
The Predator players complained that their cloaking was now worthless (a faint rainbow shimmer had been added, making cloaked Predators easier to spot), and the only compensation they got was basically a laser SMG. The cloaking effect only made it possible to spot a cloaked Predator standing still, and the Energy Flechette filled a badly-needed mid-range gap in the Predator arsenal.
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 and was, for a time, poorly received.
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.
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.
If you came through Predator, then you'll find the general mookishness of the Aliens natural.
If you came through Alien, you'll probably consider Aliens as Elite Mooks from a narrative point of view, and therefore be disappointed by how easy Predators tend to tear through them.
This difference makes the general community for the franchise a massiveBroken Base, with each side constantly debating the state of affairs.
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.
Early on in the Marine campaign of AvP2, one of your squad is kidnapped and the rest of the squad is left indecisive about how to rescue them. The player character volunteers with a simple "I'll go," but his delivery is more appropriate for volunteering to go make a beer run as opposed to walking into an Xenomorph nest alone.
No Problem with Licensed Games: The AVP games, particularly the first two, are extremely well-liked FPS games making great use of both franchises' settings and making their alien antagonists and the Colonial Marines function extremely well in gameplay terms. Even the third, which is considered a weak game, got better reception than Aliens: Colonial Marines did.
Paranoia Fuel: Know why the AVP 2 player character is called "Harrison?" It's so they could have every door in the entire game sound like it was whispering your name.
Alternate Character Interpretation: Given that Predators don't talk nor emote very much, we don't know what were Scar's thoughts after being subdued and impregnated by a Facehugger. If he knew there was a Chestburster inside of him (which he should have known very obviously upon waking up, specially after finding the damn thing dead next to him), he might have been expecting to end the hunt and reach his mothership in time to get it extracted from him, or he might have been playing straight the Zombie Infectee and denying it to himself or just pushing to postpone the inevitable outcome.
This has been happening awhile give or take, counting films, games and whatnot, but Requiem reduced the aliens to cannon fodder. Any kills they made where simply Red Shirts.
Contrarily to popular belief, the Predators themselves don't get the longer end of the stick in terms of power in the first film. Out of the three who appear in the movie, the first is killed without doing a single kill, the second goes down against the same Alien who killed his buddy, and the third one never wins a hand-to-hand fight, only excepting an instance in which he surprises a drone which believed it was going to surprise him.
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.
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, and those who hate the movie hate it for the needlessly high level of 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.
Is Lex a genuinely interesting black female lead, or a cliched adventure film girl?
Critical Backlash: There are actually many people who feel the first movie, while nothing to write home about, still is 'at least fairly okay and in any case doesn't really deserve the hatred it gets (Doug Walker notably briefly referenced it in his Shining Mini-Series review as "decent"). The second one, on the other hand, is almost universally despised.
Critical Dissonance: Internet Movie Database gives the first film a healthy 5,6/10, more than twice of Rotten Tomatoes's 21%, and most reviews are quite positive in that, thought not a great film, it gets most of what it attempts.
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 kills two Predators on its own, 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.
While most all of the humans are loathed, Adele Rousseau and Charles Weyland from the first movie have fans thanks to Adele being the closest thing to a Badass out of the humans and Weyland for his connection to the Alien films and being played by Lance Henriksen.
Wolf (the Predator in the second movie) is well liked thanks to his array of gadgets and mask, to the point many are disappointed the film didn't entirely focus on him.
Fan Preferred Pairing: Scar/Lex is probably the only ship with any significant number of fans to have emerged from the AVP movies. The producers even said they imagined Scar as a "romantic leading man", while the author of the novelization couldn't resist the temptation to introduce some jokes and teasing about it.
Franchise Killer: Requiem. Its bad critical reception and even worse fan reception together made sure that, if there was any hope of continuing the saga after the potentially interesting points opened by the first move, it got lost like tears in rain. Even although Predators revived significantly the interest of the crowd towards the Yautja and even made a nod to AvP, it's quite improbable we will get to see Aliens and Predators together on screen again.
Germans Love David Hasselhoff: The first film was unusually well received in Spain and other European countries. The second one, on the other hand, not so much.
He's Just Hiding: Some people believe that the Alien Queen from the first movie might perfectly have survived to her fate, as it was simply being dragged to the bottom of the sea by a chain when Alien: Resurrection had established that Xenomorphs can adapt to water apparently without any trouble.
Just Here for Godzilla: A lot of people who dislike the films tend to admit that the fights between Aliens and Predators in the 2004 movie were pretty damn cool, and they often watch the film specifically in order to see those creatures trashing each other around.
Love It or Hate It: While the first film is somewhat well-liked nowadays, being merely considered mediocre at worst with fans deriding mostly just the lore breaking content (sped up life-cycle, for example), the second is still mostly hated, with few fans liking the movie which was even more lore breaking than the first film by adding a competely new life-cycle that was unnecessary.
One-Scene Wonder: The Ancient Predator from the first film, specially for Predator fans.
The Scrappy: Most of the human characters in the films are hated for being flat and cliched obstructions to the crossover action. The ones in the second film get this the hardest due to being borderline stock slasher victims.
The majority of fans disliked Chet because of its outlandish reproduction method that contradicts and even outright renders the previous life-cycle obsolete and the dumb things she does, like standing idly while Wolf removes his equipment (honor is no excuse when it comes to an animal). Her design also received some criticism.
Sequelitis: Even for those who didn't like the first one, the second film was much worse in general quality.
Signature Scene: Nothing represents more this saga than the visual contraposition of a stern Predator mask and a slavering Alien head, which happens several times through the two movies. It was actually used for the first's poster.
So Bad, It's Good: To some people, the second film and its quirks (attempts on teen drama, classic horror traits, bad lighting, questionable plot and downright bad script, among many others) are pretty entertaining in a special light.
Special Effects Failure: Actually more of a Lighting Failure. The suits for AVP: Requiem are fantastic... but unfortunately, the film is so darkly lit that you can't see them.
In the original script for the first movie, after Scar is impaled by the Alien Queen, he tries to stab himself with his dagger to take the Chestburster inside of his body with him, not without speaking for the first and last time to tell Lex her earlier line of "The enemy of my enemy is my friend." Pretty much everybody who know this fact believe it would have been brilliant to see in the final film.
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.