There are anime that viewers rage and rebel against as the worst anime of all time, but then there are the ones that everyone seems to tuck away and agree to never talk about again, as if they were never made. While not necessarily horrible, these anime were generally huge letdowns as sequels, as adaptations and as what-could-have-beens.
Not terrible enough to make any "worst ofs" but just "meh" enough for audiences to simply ignore. From Gantz to Ace Attorney, these anime have as many fans that don't know they exist as they do fans that desperately trying to make that nonexistence a reality.
Tsukihime
Tsukihime is an adaptation of a visual novel by Kinoko Nasu, the creator of the Fate/stay Night franchise. The game debuted in 2000 and was adapted into an anime in 2003. The plot follows a young man who, through a serious injury, gains the ability to see Death Lines, or the connections of life and death. This power leads him into the dark secrets of his own family as well as into the world of vampires, which is currently split in two. There are five main routes in the game with more than one ending for most routes.
However, the anime, Tsukihime Lunar Legend, features only one route, which many consider the most generic and predictable route, and takes some considerable liberties when it comes to the plot, leading many to ignore its existence and stick to the game instead. However, the Tsukihime game itself got a recent remake, so perhaps a new anime adaption is on its way as well. Studio Ufotable animated the new opening sequence for the game and recently finished adapting Fate/stay Night: Heaven's Feel, so there's definitely hope that the studio could decide to tackle an anime reboot of Tsukihime, just as they took over Studio Deen's adaptation of Fate/stay Night.
Re: Creators
Re: Creators was one of the first big attempts at a reverse isekai, and for a while, it seemed like Studio Troyca had gotten it right. The blend of characters from different genres as well as general character design and production quality made the show stand out in the 2017 Fall Season until it simply faded away. In the show, high schooler Sota is casually watching his favorite anime one night when he's pulled through into another world where the main protagonist and an unknown girl in traditional Japanese armor are battling it out.
When he returns to his own world, he accidentally brings the two with him. It turns out that fictional characters from different genres have appeared all over the city and are causing chaos like only magical girls and tricksters can do. It's a cool concept but the plot and dragging storyline fails to be consistently interesting. Re: Creators is an isekai that time forgot and nobody seems keen on remembering.
Ace Attorney
Ace Attorney has been a stage play, a musical, a live-action movie, an anime and more. One would expect an anime series based on something so popular to be amazing, but the 2016 anime Ace Attorney was, at the end of it all, pretty forgettable. Game adaptations often struggle with incorporating game mechanics into anime. One of the most enjoyable aspects of an Ace Attorney game is the actual courtroom action, but the emotion and obscene amount of hand thumping that is hilarious in-game didn't translate well, and the chances the anime had to expand the story outside the courtroom didn't add the depth of character or story it should have.
The animation is also nothing to get excited about, which is odd considering the funding that should have been available. In the end, the Ace Attorney anime is simply bland, especially for newcomers to the series, which is ridiculous considering how colorful the source material is. While people had once fantasized about an Ace Attorney anime coming to life, their hopes were fortunately not dashed, but fulfilled in a mediocre way.
Steins;Gate 0
Steins;Gate is a cult classic, but Steins;Gate 0 is one of those anime that never gets a mention. Based on the video game sequel to the original, Steins;Gate 0, which aired in 2018, is meant to be an exploration of other possibilities stemming from the Steins;Gate series. In 0, Rintaro Okabe is unable to save Kurisu's life because to do so would be to invite war. Rintaro, who is a student in this timeline, suffers from trauma and guilt from his decision but eventually comes to terms with the fact he can't change the past to save Kurisu.
After a few months have passed, Rintaro meets colleagues of Kurisu's who have placed her consciousness in an android named Amadeus and agrees to help develop it. After the twisting and turning of Steins;Gate, it's no wonder that the tonal shift in 0 threw people off. While Steins;Gate is no stranger to heartbreak, the ultimate happy ending with Mayuri and Rintaro is very much at odds with the nature of Steins;Gate 0. Seeing as it is simply another possible timeline, many fans choose to ignore it.
Gantz
For being a relatively well-known work, plenty of people seem to wish the Gantz anime out of existence. The manga follows two teenagers, Kei and Masaru, who become part of an afterlife "game "after being hit by a train. In the game, a man called Gantz informs them that their lives are his and that they are to take advanced weaponry to kill aliens on Earth that normal humans can't see. There is a points system related to the missions that can lead to the participant bringing back a dead teammate or even bringing themselves back to life.
The 2004 anime takes some creative liberties that actually led to it being censored, such as lending a perverted nature to a character by having him become sexually aroused by imagining the girls in his class without clothes in enough detail that it was deemed inappropriate, even for a mature show. Many of the characters are never really fleshed out, the animation doesn't match the quality of the manga art, and the pacing of the anime makes it hard to get invested, all of which is topped off with a conclusion that is considered to be poorly done and reason enough to skip the anime altogether. There are other takes on Gantz, such as live action films and video games, that may deliver a more satisfactory adaptation and allow the anime to stay forgotten.
While none of the anime above are necessarily reviled -- it's not uncommon to find people who enjoyed them -- they nonetheless left barely a scratch on public consciousness. Tsukihime was to be overshadowed by Nase's other works, and the fact it may be getting a remake shows how inconsequential it was. Re: Creators' inability to make a dent on the world of isekai shows how badly they handled their story. Ace Attorney couldn't capture the feeling of the game, while Steins;Gate 0 left people happier remembering the end of the original anime instead. And, while some enjoyed most of the Gantz anime, the ending doesn't hold up and general consensus is to simply read the manga. None of these anime had an impact on their genre or their audience except perhaps to recommend going back to the source material. They are anime we want to forget and maybe it's better that way.