An important part of planning a series of stories is settling on the threat escalation over the course of the series. You don't start a Superman trilogy with Darkseid, an X-Men series with Apocalypse, a Green Lantern series with Paralla- oh, wait... Purely using those examples as trilogies:

• Superman should go from a non-powered (Lex), to equal power (Zodd), to greater power (Darkseid/Doomsday/Braniac).
• X-Men should begin with a threat to mutant-human co-existence (Magneto and the Brotherhood), move to a threat to the existence of all mutants (Government/Sentinels) and finally, end with a threat to all life on the planet (Apocalypse/Phoenix).
  
• Green Lantern should begin with a standard enemy of the GLs (The Manhunters), set up Sinestro as the villain for the second film with his Corps powered by fear, then move into the embodiment of fear, Parallax.
  

Judge Dredd: Judgement Day

      This film is an origin story, naturally. Dredd starts out as having recently graduated from the academy and ready to enforce the law. While not overly optimistic, he is certainly more optimistic than the average depiction of Dredd. His primary comrades are Rico Dredd and Barbara Hershey. The antagonists are the Angel Gang. It's a simple story about the three newbies having to step up and take down the Gang, who show up during a series of riots and Block Wars that keep the more seasoned judges busy. Pa Angel is eventually revealed as the mastermind behind the riots.
      Dredd and Rico are close throughout the film, being that they're brothers. They have a friendly rivalry thanks to Rico being a faster shot than Dredd. Dredd eventually discovers that Rico is corrupt either through evidence of his collusion with the Angel Gang, or from him taking bribes. The two have a duel, resulting in Rico's reaction time being slowed down though trickery, and Rico being arrested by Dredd.
      All of the Angels are killed, aside from Mean Machine Angel, who is arrested. The events of the story catapult Dredd into the spotlight in Mega City One, while also forcing him to face the fact that the justice system is not perfect, thus driving him to be the very pinnacle of law enforcement.
      The film also features Deputy Chief Judge Cal and Chief Judge McGruder, the latter of whom is something of a mentor to Hershey.

Judge Dredd: The Day the Law Died

      Drawing on the comic arc of the same name, the film centres on Judge Cal's exposure as corrupt and his villainous scheme. Cal's rise is driven, rather than ambition, by a more noble goal that grows completely out of control. Cal proposes the idea of putting serious criminals through an intensive brainwashing procedure to turn them into model citizens, a plan he demonstrates with Mean Machine and Rico. The idea is rejected on grounds of immorality, prompting Cal to secretly push forward with the plan on criminals, citizens and even judges, amassing a vast army of sleeper agents. He has Chief Judge McGruder assassinated to secure his position at the top before activating his sleepers.
      This time, Dredd is joined by Hershey and Judge Giant as he leads the revolt against Cal. Rico and Mean Machine, meanwhile, are possibly revealed to to have been in on Cal's scheme all along and faked being rehabilitated for the opportunity to kill Dredd and his allies when they come for Cal.
      With help from the street punk, Fergee, the three heroes are able to infiltrate the Grand Hall of Justice. Mean Machine ambushes them and Giant stays to hold him off so the other two can continue on. Giant receives serious wounds, but manages to kill Mean Machine. Upon reaching Cal, Dredd and Hershey are attacked by Rico. Dredd and Rico have their final battle while Hershey engages Cal. Rico is shot dead through no trickery; only Dredd's now improved speed and accuracy, and Cal is thrown from atop the building by Hershey.
      Hershey is soon elected Chief Judge and offers the position of Deputy Chief to Dredd, who turns her down in favour of remaining a street judge. Hershey understands, noting that the citizens need a shining example of law out on the streets, not cooped up behind a desk. Giant is instead named Deputy Chief Judge.
      A subplot in the film features a death cult operating in the city, heralding the end of days.

Judge Dredd: Necropolis

      The third film sees the four Dark Judges arrive from another universe. One idea is that the four are actually the same versions of the Dark Judges that appear in the main comic universe, having given up on attempting to judge that world and aiming to do so with another.
      Hershey has Dredd give training to some of the cadets, which includes Psi-Judge Anderson and Judge Perrier. Anderson is plagued with nightmares of the coming of the Dark Judges, forming a psychic link she develops with the quartet. Upon their arrival, the Dark Judges discover the cult from the previous film, who worship the villains and offer four of their members as host bodies. The Dark Judges begin a killing spree across the city.
      Anderson's visions prove instrumental in finding the Dark Judges. The first to fall is Judge Death himself, but his spirit is able to escape, forcing the city's defenders to find a way to seal their spirits. Eventually, by pushing her powers further than ever before (forced mind-reading or mind control), Anderson is able to obtain information from the cult leader that is the breakthrough the judges need to create a device to seal the Dark Judges. They use this device to put a stop to Judge Fire.
      Dredd sends Anderson and Perrier to the Hall of Justice, both to defend Hershey, and to keep Anderson and her powers safe. The duo find Hershey being attacked by Judge Mortis. Hershey gets her moment to shine when she puts her boot through Mortis' chest, stunning him long enough for the others so capture him.
      Dredd, meanwhile, engages Judge Fear, leading to a live action recreation of the infamous "Gaze into the Fist of Dredd" moment from the comics. Once his compatriots are dealt with, Death attacks the Hall himself while Dredd makes his way over. Perrier is killed defending Anderson, who is captured by Death.
      Hershey and Giant join Dredd in hunting Death down to save Anderson and other Psi-Judges that have been captured over the course of the film. Death manages to evade the trap when his current body is killed and he attempts to possess Anderson's body, noting his long-held desire to do so if the Dark Judges are established as the ones from the comics. Anderson is able to force Death out of her body, though only after she receives numerous wounds to induce a rush of adrenaline. Death is captured and placed into containment with his comrades.
      The trilogy ends with a memorial for fallen judges, which acknowledges those killed in previous films. After this, a recovered Anderson joins Dredd as he heads out on patrol to continue his eternal battle against injustice.