Most anime is based on manga. Sometimes, this results in long, meandering series with endless filler arcs, like One Piece, Naruto, and Bleach. Sometimes, the series are shorter, lacking filler but still shackled to the pacing and plot lines of the original manga. Are you seeing a problem yet? Not all anime is based on manga, though - some series are totally original to the studio, and others are based on video games, light novels, and literature.
Most of the time, original anime is way, way better than anime that’s tied down to a manga. Death Note fans, put away your notebooks, Naruto fans, stow your kunai - your favorite anime might be good, but it has a whole host of problems it wouldn’t have had if it weren’t based on a manga. So why is original anime better? Well, for one thing you’ll never have to argue with anybody about which version of Victor Nikiforov is canon, because there’s only one version. For many other things, read on.
While some would argue that manga is literature, anime studios do get their inspiration from actual books. Like, you know, the kind without pictures. Howl’s Moving Castle, one of Studio Ghibli’s many masterpieces, was based on a fantasy novel of the same title by Diana Wynne Jones.
This encouraged a lot of reluctant readers to pick up a book, and it made for an amazing story. Before it was an anime, Welcome to the N.H.K. was a novel by Takimoto Tatsuhiko, and the resulting anime is devastating while still being hilarious.
Some anime are so different from their manga versions that they’re practically a new series. While this isn’t as common as it used to be, this can be a huge problem for fans of older series.
Take Fruits Basket, for example. The main antagonist, Sohma Akito, is completely different in the "animeverse" and the "mangaverse." First of all, in the anime, he’s a man. In the manga, she’s a woman who was raised male by abusive parents. Second of all, Akito in the anime is controlling and abusive to his family because in order fulfill his role as the family deity and keep everyone alive, he must sacrifice his health. He resents this deeply. In the manga, it’s because she was taught this behavior by her abusive mother as a means of keeping the family from abandoning her.Both Akitos (Akiti?) are interesting in their own right, but they’re completely different characters. Fruits Basket fans have to individually decide which version they accept, which can make it hard to discuss the series if they're not on the same page.
Suppose your favorite manga is finally being turned into an anime. You’re super excited, especially when your favorite character finally shows up. How could this go wrong? But that excitement turns sour when you hear your favorite character speak. That’s not the voice you imagined for her! Not only that, but it’s completely out of character!This may seem nitpicky to some, but for hardcore fans, this can really mar the experience of an anime adaptation. For some, Mamoru Miyano’s portrayal of Light Yagami is just wrong, because that voice just doesn’t match the one they heard in their head when they read the Death Note manga.
Meanwhile, nobody thinks Mamoru Miyano’s portrayal of JJ Leroy is wrong. They can’t, because no one knew who JJ was until they heard Mamoru Miyano shouting "it's JJ STYLE~!"
Let’s say you’ve never seen Fullmetal Alchemist, and you want to fill that gap in your anime knowledge bank. Sounds easy enough, right? Wrong, baka! Remember - there are two Fullmetal Alchemists! How do you choose? You could pick Fullmetal Alchemist: Brotherhood, because it’s based on the manga and is regarded as the more faithful adaptation, but you could also choose the original series because you kind of remember seeing it on Toonami back in the day.
Or you could watch both, but unless you’re really, really into watching Edward Elric yell, you probably don’t have time for that. You might just decide it’s too confusing and forget about watching FMA all together.
Brotherhood was created because the first series bore little resemblance to the manga. While both series are good in their own way, the existence of both can sometimes be more trouble than they're worth. With titles created in an anime studio, this kind of thing just doesn’t happen.