These are incredibly important for the history of anime.
It’s not often we get series that reshape entire genres. Often when that happens, we don’t even realize it until years later.
If you want to watch something so influential you still see its impact today, here are some series that were so successful they changed the entire field.
Neon Genesis Evangelion is so influential that it didn’t just change its own genre — it changed multiple. After airing in 1995, it spawned an era of highly complicated, deeply philosophical series that spanned into the mid-00s.
It also heavily influenced the mecha genre — it was mostly associated with horrors of war before. After Evangelion, many series tried to focus more on the psychological aspect behind a singular pilot character.
K-On!
The “cute girls doing cute things” genre was a thing even before K-On! That said, it is absolutely an anime that changed the entire genre. Before it, the comedy of those was largely absurd and random.
K-On! was the first major hit of the genre that focused on the “feel-good” moments and followed a group of girls in a school club. The latter especially is something that many viewers can’t imagine the genre without — but the trope got popular after K-On!.
Madoka Magica
The magical girl genre was always perceived as mostly aimed at young girls. Yes, darker takes on it existed before (and some of them were even particularly successful).
However, “dark take on magical girls” didn’t exist as a properly formed subgenre before Puella Magi Madoka Magica (Mahou Shoujo Madoka★Magica), which, after becoming a major hit in 2011, spawned a ton of other series trying to deconstruct the genre.
The Melancholy of Haruhi Suzumiya
Just like K-On!, The Melancholy of Haruhi Suzumiya (Suzumiya Haruhi no Yuuutsu) is partly famous because of its amazing visuals by Kyoto Animation. That said, its contents are also pretty iconic.
The anime has basically codified the genre of “high school club slice of life romcom.” Other tropes, such as the mystery aspect and a cynical protagonist, are usually followed as well. Many of the later series of the genre often include supernatural elements too.
Mushoku Tensei
This is a very unusual example. While the anime for Mushoku Tensei: Jobless Reincarnation (Mushoku Tensei: Isekai Ittara Honki Dasu) only aired in 2021, it influenced many isekai series — of reincarnation subtype — some of which came out before it. This sounds like a contradiction, but the explanation is fairly simple.
The source material behind Mushoku Tensei — more specifically, the web novel that was later turned into a light novel — started publishing in 2012, way before many other isekai series that got an adaptation before it. It became an instant hit and changed the scene for the genre forever.