The isekai anime genre may be reaching saturation, but there are still noteworthy titles.
The term 'legendary trio' is often used to describe the influential giants in the anime world. In the Anime universe, these are typically renowned shonen series like Naruto, Bleach, and One Piece. Since then, the concept of a 'trio' has emerged in other subgenres, including isekai.

Formerly, the 'king' of this genre was arguably Sword Art Online – an anime series revolving around players trapped in a virtual reality game world. While it was famous, many viewers at the time didn't categorize Sword Art Online as isekai. Yet, today, when discussing the origins of isekai's success, everyone surely thinks of the first SAO.

The former trio of isekai anime was once identified by a chibi-style anime show called Isekai Quartet. This series is a crossover between the most famous isekai anime: RE:Zero, Konosuba, Overlord, and Saga of Tanya the Evil. Konosuba is often seen as a humorous parody of the isekai genre, so the other three series are considered the real 'trio.'

However, fans quickly named new series to replace RE:Zero, Overlord, and Tanya. Among them are The Rising of Shield Hero, That Time I Got Reincarnated as a Slime, and Mushoku Tensei.
Why are the above 3 series considered the 'trio' of new-generation isekai anime? The Rising of Shield Hero premiered in 2019 and quickly garnered a large audience. The series revolves around Naofumi Iwatani, a young man summoned to another world and hailed as a hero.

What's interesting is that in this anime, Naofumi eagerly desires to return to his old world, unlike most isekai protagonists who never entertain the idea of going back. The new world Naofumi finds himself in resembles an MMO game, reminding many viewers of Sword Art Online.
On the other hand, the success of Slime Reincarnation comes from its groundbreaking storyline. The story follows Satoru Mikami, an ordinary office worker reincarnated into another world as a Slime. After releasing a dragon imprisoned for 300 years, he is bestowed with a new name, Rimuru Tempest.

Despite being an isekai anime, Slime Reincarnation also emphasizes other elements such as combat systems, world-building, character development, and plot, avoiding monotony for viewers. The success of this series demonstrates that the isekai genre can still achieve great success even in a saturated market.
Mushoku Tensei, on the other hand, is a controversial nominee. Despite its popularity and certain success, this anime still doesn't sit well with some audiences. The series follows a typical isekai protagonist: dying in a car accident and reincarnating into a heavily fantasy-infused world.

Mushoku Tensei may not compare in content to the above 2 series, but it still caused a major stir upon its release in 2021. Will we get to enjoy higher-quality isekai masterpieces in 2022, replacing the positions of the aforementioned series? While not easy, isekai fans are still hoping for the answer to be 'yes.'