Star Trek fans need to do what us Highlander fans and a great majority of Star Wars fans do: If you don't like it, get angry over it for a very brief period of time, then go into a severe drinking fit, and then pretend the sequels you don't like don't exist! ... It's called selective amnesia, and it works wonders for nerds.
Established movie franchises tend to have Fanon Discontinuity imposed on them, especially whenever crappy sequels rear their ugly head.
Note 1: Do not include examples based only in adaptation. A movie adaptation can not be discontinued since it is not part of the continuity of the original. You can discontinue a sequel of the adaptation but not the actual adaptation. To a lesser degree you can discontinue PARTS of a movie.
Note 2: Ignoring certain works of a person or company so they're "still good" is also forbidden as that would be ignoring real life events (which we are not doing here).
Note 3: Do not post personal examples. Examples should only be of groups of fandoms.
The Alien fandom has several groups of fans who disavow various parts of the franchise.
And others only consider Alien³ canon if watching the work print version of the film.
A number of fans also consider the Dark Horse Comics' Expanded Universe (which includes Earth War, the continuation of Ripley, Newt and Hicks' storyline after the second film) canon, and dismiss any movies after Aliens.
Alien: Resurrection also gets this for being bizarrely quirky and an amped-up copy of the original film's plot. Other fans are open-minded enough to acknowledge both 3 and Resurrection.
Some fans refuse to believe that the two Alien vs. Predator films were made, the first of which was directed by Paul W.S. Anderson of Mortal Kombat and Resident Evil fame. Others accept only the first AVP, which at least tried to retain the atmosphere of the respective series, while rejecting the second for being squicky without actually being scary. There are others who like Requiem, and ignore AVP for being a PG-13 movie marketed to kids.
Prometheus has been viewed by some fans as this, not only for being a largely-inconsequential addition to the overall mythology, but for dropping a metric load of unanswered questions and shoddily-written characters into a plot that has little-to-no purpose other than explaining the origin of the "Space Jockey" seen in the original film.
In the first film, Neo was a man told that everything he knew was a bunch of raining green data and was thrust into a much more dangerous new world. The audience learned right alongside him, and the smirk he makes in the dojo fight with Morpheus is an example. In Reloaded, Neo has become a Boring Invincible Hero who can kick the asses of 100 Smiths and remains a totally emotionless robot through the whole movie, even when he's making out with Trinity.
It can be noted however that many feel Reloaded is the better of the sequels, while a handful think it even surpasses the first film.
A few Star Wars fans hate the Ewoks so much that, nearly three decades later, they still disavow Return of the Jedi as a legitimate episode of the franchise - which of course is pretty much impossible, because that's the film that resolves the entire franchise!
Don't forget that there are still Luke/Leia shippers out there who disavow pretty much Return of the Jedi in its entirety. Well, maybe not the Jabba's Palace sequence, even if it does score Han/Leia points, but Luke/Leia had an instant Non-Standard Game Over.
Fans aren't the only ones who want to pretend Ewoks never existed, as you'll discover when you read just about anything Anthony Daniels (C-3PO) has to say about them.
Ask anyone who saw the original trilogy first what they thought of the prequels. You are likely to be punched in the face and informed that there is no such thing, but it's so worth it.
Lucas mentioned that his work on ''Robot Chicken-Star Wars' was his way of apologizing to the fans for anything they don't like about the series. Apology accepted.
Star Wars has all kinds of Fanon Discontinuity groups. Some say the Prequels and the Clone Wars movie never happened In-Universe. Others say that only the movies ever happened, and that the Expanded Universe is non-canon. Still others say that nothing after Empire Strikes Back happened. Then we get into the groups that dis the continuity in regards to certain parts of the Expanded Universe, like the Jedi Prince series, the New Jedi Order series, the Legacy era, and so on.
Lucas once said that the Jedi, as seen in the prequels, were allowed to have sex, but weren't allowed to form attachments. Just about everyone has ignored this, from fans to EU creators, for obvious reasonsnote Partially because it's not as fun writing fanfic if it's just sex, and partially because some people don't like the idea of sex without love, or even a strong "like".
There is also the fact that unlike Star Wars, Indy's EU is fairly obscure, so it's no surprise many fans not only don't think of any but the movies as canon... they don't even know about the novels, comics (specially the terrible 80s Marvel comics), park rides, tabletop games and videogames. Opinion is perhaps more divided about the prequel TV series, the only non-movie installment that gets some references in fan fiction.
Plenty of The Crow fans only consider the first film in the series, starring Brandon Lee, worth watching, although to an extent City of Angels has a fan base too.
With The Pink Panther films, there are fans who only count the films Peter Sellers was in as canon. Trail of the Pink Panther is an interesting case here, since it was assembled from deleted scenes and flashbacks of Sellers two years after his death. If the film doesn't count on its own, then the deleted scenes can be seen as canon in their original context of material dropped from The Pink Panther Strikes Again. Even MGM/UA has encouraged the Sellers-only approach on occasion; the Pink Panther Film Collection DVD box set from 2004 only included the Sellers films they owned the rights to. (They don't currently own the Return of... rights).
Many people wish they had never heard of Home Alone 3, due to the absence of Macaulay Culkin, its mediocre quality, and the lack of genuinely funny villains, or Home Alone 4 simply because it sucks. A few even wish they hadn't heard of Home Alone 2 because it's similar to the first one, just recycled in some other town.
Understandably though, Macaulay Culkin would have been gotten too old to be able to keep up the part of Kevin by the time of Home Alone 3. (This was mocked on an episode of The Critic in which Jay Sherman reviews Home Alone 5, and the McAllisters are horrified to learn that they've - once again - left Kevin home alone because "he's only 23!")
Terminator 2 featured a positive ending where John Connor not only survives, but manages to prevent the global nuclear apocalypse that would nearly wipe out humanity from ever happening. Terminator 3, on the other hand, takes a Shoot the Shaggy Dog approach to the previous movie and flat-out states that Judgment Day is inevitable, rendering every action taken in the previous movie a waste of time, including the Heroic Sacrifice of one of the well-intentioned programmers who would have originally brought the apocalypse about. No mention was made that this inevitability renders the entire time traveling kill-your-enemy-before-the-war theme of the series equally pointless. As a result, many fans insist that the series ended after the second movie, or that the more positive The Sarah Connor Chronicles TV series is the only follow-up. Never mind that it was hinted at being inevitable the entire time - John sent his own father back in time, which couldn't happen without a Stable Time Loop, and thus a more or less stable timeline..
And then there's the people that refuse to acknowledge even Terminator 2, believing that it screws up things just as badly, if not worse, than everything that came after it.
The fourth movie, Terminator Salvation gets some discontinuity because it follows the events of the third movie, changing the focus of the series (future war against the machines instead of the present day).
Salvation also gets some discontinuity because it contradicts The Sarah Connor Chronicles, most notably through the absence of any reference to Derek Reese. Some fans who otherwise wouldn't have had an issue with it choose to ignore it simply because keeping it would make it tricky to keep the series in canon as well.
Numerous fans also throw out Nemesis, due to (among other things) the appearance of a sister race of the Romulans that had never been featured or mentioned before, the crew acting like they had never met another Soong-type android before, and Data dying even though it could have been easily avoided using other pieces of Treknology. On a lesser scale, fanfic writers Retcon the ending to allow Data to survive through various means (from swapping his mind with B4 to being blown into an Alternate Universe). In fact, the comic book series "Countdown", a lead-in to the 2009 Star Trek movie suggests EXACTLY that Data's neural patterns were downloaded into B4 (the film itself makes the same suggestion, although perhaps not to the same degree).
Star Trek: Insurrection is sometimes ignored simply for generally being considered bad, although this is easier as no canon-changing events occurred.
Then of course, many fans will ignore JJ Abrams' Star Trek films, for wrongly assuming that it "wipes out" the events of every series other than Star Trek: Enterprise, but also for taking Star Trek from 'vaguely plausible' to 'no idea how physics works in any way' and for a perceived "dumbing down".
A number of Spy Kids fans agree that the less said about the third film, with its poor writing (including an ending which made no sense whatsoever by failing to explain how the virtual reality creations ended up in the real world) and a stupid "3D" gimmick, the better! It doesn't help that it was a Dolled-Up Installment made from a totally unrelated script.
Some would also say there wasn't a second film either.
And the fourth is possibly the least well-received of the bunch.
Some in the Highlander fandom disregards all sequels. It helps that each installment, besides quality problems, ignores events outside the first movie. (The only exceptions: Highlander Endgame is a cross between the first movie's and the TV series' continuity, and the Direct-to-VideoHighlander The Source follows the events of Endgame). Those who enjoy most of the movies will still adamantly ignore Highlander II: The Quickening, which has little more than a few names in common with the Highlander universe. Highlander 2 may be the most hated sequel ever made.
Other Highlander fans decide to ignore all the films for the sake of a protagonist who KNOWS how to handle a sword - that is, for Highlander the series.
In short, there should've been only one.
Fans of the Inheritance Cycle found the live-action movie made from their series so radically inaccurate and generally botched it's become a Running Gag through some of the fandom to "disown" the movie, or simply pretend it doesn't exist.
All the sequels to Jaws are disregarded by much of the fandom, in part because of the sharp drop in quality with each entry: the mediocre Jaws 2, the cheap but counterproductive "3D" gimmick in Jaws 3D, and the ridiculous Voodoo Shark concept and horrific execution in Jaws: The Revenge.
As far as many fans of the Mission: Impossible TV series are concerned, whatever those movies were, they certainly did not depict the real IM Force, and that definitely wasn't Jim Phelps. Besides, the films completely ignored the elaborate scams aimed at fooling the bad guys which were the entire raison d'etre for the original series.
The Godfather Part III is widely perceived to be inferior to the first two movies made during the classic New Hollywood era. With a convoluted plot, a love story featuring Kissing Cousins (Mary Corleone and Vincent Mancini), a former main character getting McLeaned (Tom Hagen), and arguably some Badass Decay (Michael Corleone), this sequel alienated a great deal of fans, many of whom prefer to pretend this never happened. Some viewers point out that it's still a decent movie, just not on par with The Godfather I and II. Others use Brain Bleach to forget its existence. In any case, when people refer to the great The Godfather movies, they more often than not mean the first two.
Word of God says that the movie was never intended to be on the epic scale of the first two, and in fact the original title was the spoilerific The Death of Michael Corleone before Executive Meddling took over.
An ironic reversal of what happened with Part II. The studio were dead set against simply calling it The Godfather Part II — "Boring! More of the same!" — but Coppola dug in, insisting that it was a continuation of the original movie and not a separate story. Fifteen years later he wants to make The Death of Michael Corleone, and — "You want to call it what? You're insane! The Godfather is the most acclaimed franchise in cinema, and this is part three!" Cue the crushing disappointment when it turns out to be utterly unlike parts I and II. (Of course, as the original entry points out, there were other problems.)
The ending of Pretty in Pink outraged many, and it is generally ignored in favor of the original ending, which was thrown out because Molly Ringwald, the star of the movie, suggested the new ending. John Hughes was notably displeased with the revised ending.
And then there are some that prefer to ignore X-Men Origins: Wolverine, because it was poorly executed and has a lot of continuity errors with the main series. The two movies that followed even ignored it (although The Wolverine briefly includes a scene of Origins in a flashback).
The revival movie flat-out says everything after 1981 never happened, although there are references.
Invoked in The Nostalgia Critic review of The Neverending Story 2 in which he says it's a good thing there was never another sequel, even though there actually was, before turning on the theme from the movies to drown out the complaints to that effect. He ended up reviewing the third anyway.
The Neverending Story 3 is so awful that fans of the original like to pretend that it doesn't exist. It's often placed on Worst Movies of All Time lists.
Many (most?) Anne Rice fans pretend there was only ever one Vampire Chronicles movie made, and it was the one in 1994 starring Brad Pitt and Tom Cruise.
Fans of The Mask almost unanimously loathe it's sequel mostly because of it's overwhelmingly horrible quality and lack of Jim Carrey.
Many who watched A.I.: Artificial Intelligence feel that the movie should have ended with David at the bottom of the sea in front of the statue of the Blue Fairy and wishing he was a real boy, rather than the overly-sugary last 10 minutes of the movie, which feels awkwardly tacked on in any case.
Most fans of Dragonheart agree that there is no sequel.
Though technically a sequel to The Rocky Horror Picture Show, being that it takes place after the prior film and even subtly references it a number of times, most fans would rather consider Shock Treatment to be a separate entity entirely. Even series creator Richard O'Brien has claimed that the Brad and Janet of that film are not the same characters previously seen in RHPS - which is more or less universally accepted, due to their vastly different physical appearances (Jessica Harper bears absolutely no resemblance to Susan Sarandon) and failure to recognize characters that look *exactly* like the castle inhabitants.
Quite a few fans like to pretend that Airplane II: The Sequel never happened. Not so much for quality reasons as they just prefer to remember Airplane! as a standalone classic and aren't big on the absence of the ZAZ team. Those who do admit its inevitably not on par with the original but is very funny on its own.
Fans of the American Pie series refuse to acknowledge the straight-to-DVD installments and skip to the seventh entry (American Reunion).
Many fans of The Three Stooges will tell you that the boys called it quits after Shemp's death in 1955. A substantial number will go further, insisting that the Stooges broke up after Curly's stroke in 1946.
Some Planet of the Apes fans choose to ignore the final original film, 'Battle for the Planet Of The Apes', due to the bad quality of the plot and the writers' insistance on reinforcing the circular timeline theory that not all fans agree with.
Many fans of the franchise tend to accept only the firsttwoSuperman films as worthy of canon, furiously denying the validity of furthersequels. In fact, Superman Returnsattempted to play into the fans little game by also ignoring films beyond Superman II but it also fell prey to the ostracism.
Some fans of the Fast And The Furious consider 2 Fast 2 Furious to be this, due to the entry's Genre Shift to heist movie to urban action movie and most of the franchise's fans not liking the new characters.
Many The X-Files fans will inform you that I Want to Believe never happened.