The Scarecrow, Dr. Jonathan Crane, is a Mad Scientist dedicated to the study of fear. First appearing in Batman: Arkham Asylum, he participates in Joker's plan to take over the titular asylum and attempts to Mind Rape Batman several times with his fear toxin. Upon his final defeat, he threatens to contaminate Gotham's water supply with the toxin simply to spite Batman. Scarecrow returns in Batman: Arkham Knight as the Big Bad. This time around, he takes advantage of the power vacuum created by Joker's death and unites all the remaining villains against Batman. After a demonstration of his newest fear toxin causes a diner full of people to rip each other apart, Gotham is evacuated, allowing Scarecrow to take over a chemical plant and manufacture a fear bomb powerful enough to take out the eastern seaboard. He even gleefully speculates that the toxin will carry on the air across the county, creating a "nation of fear." Foiled in this, he steals a superweapon called the Cloudburst and uses it to drive all of Gotham temporarily mad with fear. He also has Barbara Gordon kidnapped and leads Batman to believe that his toxin caused her to kill herself. He then manipulates Commissioner Gordon into betraying Batman, and, after the Commissioner goes against orders and seemingly kills him, Scarecrow forces Jim to watch as he drops the still-living Barbara off of a building. In the end, he captures Batman and forces Gordon to unmask him on live TV. He then plans on letting Batman go so he can watch as Gotham is torn apart and everyone he loves is hunted down and killed. All of this was done to completely destroy the myth of the Batman as a savior, and force everyone to experience true fear by destroying their symbol of hope.
Due to being a four-game story, there are details (Batman and Joker's Titan Poisoning in City, Deathstroke's sudden appearance in Knight) that won't make sense unless you've played the other ones.
Some plot points require at least some cursory knowledge of the comic books, though the games rectify this somewhat by giving you profiles regarding characters, but still occasionally falls into this trope, particularly in the case of Jason Todd, whose presence was almost completely absent until Knight.
The games are one of the darkest adaptions of both the Batfamily and their rogues gallery, so obviously some (especially fans of a Lighter and Softer or outright Campy Batman) are drawn away from them. Each game has a Nightmare Fuel folder for a reason, not to mention that the games don't shy away (they actually zoom in) from Batman breaking limbs instead of just quick takedowns like most movies do.
Another reason is that, while even Christopher Nolan's movies end on a note of hope as does the DCAU, the endings of the Arkham games tend to be far more bitter than sweet, with Batman consistently shown as a Failure Hero and the finale of Knight ends with his secret revealed to the world and the end of his career as Batman, with the DLC implying that his sidekicks pick up and fight the remaining villains. The Arkhamverse Batman ends his career not on a note of triumph or Heroic Sacrifice but in defeat and exhaustion.
Ensemble Darkhorse: The Arkhamverse version of Harley Quinn is one of the more popular secondary villains, going from a supporting role in the first two games, to being the Big Bad of her own DLC, to being fully playable in Arkham Knight. Harley's portrayal in the games also raised to profile of the comics version.
Scarecrow. His nightmare sequences in Arkham Asylum were considered some of the best parts in the game. When he was absent in Arkham City, people were disappointed. This may have something to do with him being promoted to Big Bad in Arkham Knight, where he is subjected to a lot of Adaptational Badass-ery.
Even Better Sequel: Arkham City is considered by some to be the overall best game of the franchise especially since it built on Asylum's features while adding crucial features (namely the iconic gliding and grapnel traversal mechanic where in the first game it was merely scripted), more combat and stealth options (varied combo finishers, multiple environmental takedowns), amping up the difficulty (with armored thugs and jammer-packs), adding Catwoman as a playable character, having one of the most praised boss fights in the franchise (Mr. Freeze), and for its rich storyline with its shocking twists that most Didn't See That Coming: the Two Jokers/Clayface reveal, and the Joker's death at the end.
Evil is Cool: The villains are usually the most well-written characters featured in each game. The Joker, Scarecrow, and the Arkham Knight are probably the best examples.
Occasionally jumps to Hypocritical Fandom, as people tend to ignore any errors between Asylum and Citynote Such as Hush's and Strange's chararacter bios, while declaring Fanon Discontinuity whenever a Origins event doesn't exactly match a bio in Asylum.
Foe Yay: All four games illustrate this in Joker and Batman's relationship. Starting early in Batman: Arkham Asylum with Joker: "Tell me Bats, what are you really scared of? Failing to save this cesspool of a city? Not finding the Commissioner in time? Me, in a thong?!" and that the premise of the whole night was a party Joker threw for Batman. Then continuing in Batman: Arkham City with the increasing phone calls from Joker to Batman, the final death scene with Batman carrying Joker out in his arms, and Joker's swan song to Batman. Given their beginnings in Batman: Arkham Origins when Joker's obsession with Batman begins, including his Red Hood story and his mention of "meeting someone very special earlier tonight", and another song for Batman during the credits. And finally culminating in Batman: Arkham Knight with Hallucination!Joker mentioning over and over again being inside of Batman, the heavy indicators that Joker's death affected him so much that he could never return to normal (not even Talia's death is mentioned that much), and the serenade number Hallucination!Joker performed with a little help from Johnny Charisma. Catwoman even makes a dig at the relationship in Knight, and how Batman should stop mourning him and "find new maniacs". The whole Batman: Arkham Series arguably reads like an overall story of Batman and Joker's relationship.
While all the games are generally well reviewed and well received, the prominence of the Joker as really the primary bad guy among everyone else has been criticized, as it lead to the detriment of other villains having a chance at truly taking stage. But this has been a wider-franchise problem for Batman on the whole, since the Joker is so inherently charismatic that he has overshadowed others for a long time in the comics, the cartoons and avoided doing so in The Dark Knight Trilogy only because of Heath Ledger's death. The Arkham games, being a tribute to Batman in different media, could not help over-representing the already over-exposed Joker.
In most Batman media, the Foe Yay between Batman-Joker is subtext and only becomes relevant to the plot in stories where Joker is the main threat. In the case of the Arkham games, it worked well in Batman: Arkham Asylum because the game's smaller island facility setting, overall Bedlam House atmosphere and the main plot (which is the only time Joker is actually involved at the helm) fits that motif better. But in the sequels, the main plot and threat is Hugo Strange's Protocol 10 (and Ra's Al Ghul's plans for Gotham) and Scarecrow's plans to unleash fear toxin and humiliate Batman. In both cases, the Joker's involvement in the plot, and the time devoted to their relationship becomes a Romantic Plot Tumor since every game ends up offering some commentary on their rivalry and mutual obsession. Origins had a good general plot which advertised the Joker as merely part of Black Mask's general scheme, and comics fans were excited thinking Black Mask was going to be a more prominent villain than he was, only to find out that Origins was in fact about Joker's debut in the criminal underworld and the start of his and Batman's "relationship" while Black Mask gets submitted to a thoroughly humiliating Adaptation Decayending with him being killed off brutally in Arkham Knight's Red Hood DLC, while begging for mercy.
The series and its poor track record with making good boss fights is another example. The original game was criticized for reusing the same bullfight setup with Bane or opting for thug attack waves instead of direct battles for most of its encounters with any other boss fights being deemed lackluster or boring (with the exception of the penultimate battle with Poison Ivy). While City was praised for having the famous Mr. Freeze showdown and more original boss fights, overall it remained a criticism due to the presence of several (albeit mostly justified) Anti-Climax Boss segments. Origins, a secondary game made by a different studio, was widely praised in its handling of boss battles, making it appear to be an inversion at first. However, Knight, with a few exceptions (notably fighting Riddler in a giant robot suit and tag-teaming with Nightwing to take down Killer Croc in the DLC) lacked several proper boss fights while many combat encounters with thugs and Batmobile tank battles filled their place.
Genre Turning Point: For licensed games in general. Before Arkham Asylum, it was common for studios to invest money in AAA license titles that were often movie tie-ins. The Batman Begins video game is a famous example as is an abortedThe Dark Knight game, and the many Harry Potter games which adapted the movies rather than serve, as the Arkham games, as an adaptation of the license tailored to the video game medium. While some movie tie-ins do exist such as The Amazing Spider-Man, they are more or less relegated to mobile games, and indeed the upcoming Spiderman PS 4 is following Arkham's approach in adapting the license to the game rather than make a movie tie-in. Most famously, where The Lord of the Rings had movie tie-in hack-and-slash licensed games, for The Hobbit, Monolith Studios made a game-centric adaptation of the licensed property, leading to the critically acclaimed Middle-earth: Shadow of Mordor. Monolith explicitly cited Rocksteady as their inspiration noting that it raised the bar for adapting licensed properties by insisting that it work first and foremost by providing entertaining gameplay.
Good Bad Bugs: For both Asylum and City, Batman's quick ground takedown consisted of straddling a prone thug and punching him in the head, but due to the target rolling back and forth while dazed, the combat animation could randomly flip him around and have Batman hit him straight in the pelvisor tailbone. While Origins tried to correct this mistake, it also introduced a variation where Batman leaned down and punched the victim's ribs, which sometimes meant he accidentally shoved his face into goons' crotches. It was finally fixed in Knight, where Batman leaps to the side before striking.
Harsher in Hindsight: How shall we put it? The Joker himself has been a Death Seeker from the very beginning of the series. In Arkham Origins, he tries to shoot himself in the head in order to end it all, but Batman stops him from doing so for reasons he can't comprehend. In Arkham Asylum, after the Joker says, "I have nothing left to live for," he does shoot himself, but with a Titan formula gun to the throat. His "suicide" is very painfully slow, as it takes a year for the Titan poisoning to course through his bloodstream before his death and its nature complete their course at the end of Arkham City, in fulfillment of his deserving to die as a monster, all the while Batman is unable to intervene with him.
Headscratchers: How does the explosive gel not blow up inside of the can when Batman presses the button?
The comments section on Destructoid had a Running Gag about which infamous C-list Batman villains they'd love to see in the Arkham games, with the most common target for ridicule being Professor Pyg. Lazlo Valentin would eventually get a sidequest to himself in Batman: Arkham Knight.
Like You Would Really Do It: The Arkham VR game starts off with the death of Nightwing, and near the end Killer Croc takes a bite out of Robin, which few people believed would stick. It also takes place between City and Knight, and is a hallucination/dream sequence.
No Problem with Licensed Games: Not only are these considered the best Batman games ever made, not only are they considered to be among the best licensed games ever made, they're often placed in the top tier of character action games ever made, period. They are arguably the trope's Most Triumphant Example. Related to this is...
Only the Creator Does It Right: Rocksteady Studios developed the Arkham IP and did it so well their popularity exploded. So when Batman: Arkham Origins was announced as being developed by Warner Bros. Montreal — essentially a stop-gap game to fill time while Rocksteady was busy making Batman: Arkham Knight — there was genuine concern about how the game would turn out. However, despite lacking serious gameplay changes and the polish of Rocksteady's games, Origins was well received as an expansion of the Arkham universe, with some consider it to have a very compelling story, dialogue and more varied boss battles than the first two games. Furthermore, Knight's status as a Contested Sequel and the problems and controversy of its PC Port has led to Arkham Origins being better regarded by some.
Polished Porting Disaster: Return to Arkham has much better character models and graphics, it adds some new details to the environments, but comes with the cost of an unreliable framerate and downgrading of some other effects. According to some, the framerates are actually worse than before.
Patches seem to have improved the framerates, leaving only some graphical downgrades which are barely noticeable unless played next to the older versions. At the moment, the remasters seem to lean towards the "Polished" side of the spectrum.
What Do You Mean, It's Not for Kids?: It's made perfectly clear that this game series was not aimed at children, with Arkham Knight even getting slapped with an M rating, but that didn't stop kids from purchasing it. The series is full of brutal death, intense violence, psychological horror, sexual content, corruption, and of course Batman and his villains acting more nightmarish than ever before, all packaged along with extremely dark themes and storylines that can be chilling from their concepts alone. There's a very good argument to be made that they are the darkest Batman adaptations ever made. Unfortunately, there were still some families that thought it was okay to buy for kids simply because it had Batman. Needless to say, people were shocked.
This pretty much sums up many fans' reaction to the fact that Commissioner Gordon keeps getting recast. Across the whole franchise, he's had five voice actorsnote Rick D Wasserman voiced a young Gordon in Asylum, but that was Time-Shifted Actor, going from Tom Kane in Asylum, to David Kaye in City, to Michael Gough in Origins and Blackgate, to Chris Cox in Assault on Arkham, to Jonathan Banks in Knight.
There's also the matter of Troy Baker and how many different characters he plays- first he's Two Face and Robin in City, then Joker in Origins, and then the Arkham Knight/ Jason Todd in Knight. That's overall five different characters done by one actor, which had several fans aghast, especially since Baker has appeared in nearly every major video game released in the past four to five years.