The first well-known isekai title was The Familiar of Zero back in 2004. Until now, isekai series mostly comes from light novel than manga, from Sword Art Online, arguably one of the best isekai series to That Time I Got Reincarnated as a Slime, the best-selling isekai series.
During the early mid-2010, the isekai genre become so popular, thanks to Sword Art Online anime adaptation, which open the ways for more isekai anime to be adapted into anime. While it started to generate backlash, isekai also very welcomed in both Japan and the overseas.
What about manga? Since a most isekai anime used light novel as its source material, there are a lot of isekai manga adaptation. When there are original isekai manga, most of the time, isekai manga is adapted from light novel. It's actually better for the fans, so we can choose which ones is fit the most with us.
Now, since we talk about isekai manga, what is the best isekai manga you've read? I think every people will have their own opinions. Rather than argue each other, let's see what Japanese think about it. The Japanese portal, Rank-1 Media conducted a poll for the most favorite isekai manga of 2022. The result is not much surprising, but there is one manhwa in the top 20. Well, here is the result for the most favorite isekai manga according to Japanese.
20. I Opened Up A Cafe In A Different World.
Published: 24 October 2014
Publisher: Alpha Police
Genres: Gourmet, Slice of Life, Supernatural
19. Isekai Ojisan
Published: 29 June 2018
Publisher: Kadokawa Shoten
Genres: Comedy, Fantasy
18. Abandoned Empress (Manhwa)
Published: 11 June 2017
Publisher: D&C Media
Genres: Drama, Fantasy, Romance
17. The Strongest Sage with the Weakest Crest
Published: 27 June 2017
Publisher: Square Enix
Genres: Action, Fantasy, Reincarnation
16. Around 40 Kenja no Isekai Seikatsu Nikki
Published: 21 April 2018
Publisher: Kadokawa
Genres: Action, Adventure, Fantasy, Reincarnation
15. Hamefura
Published: 28 August 2017
Publisher: Ichijinsha
Genres: Reverse Harem, Comedy, Romance
14. Isekai Cheat Magician
Published: 26 December 2016
Publisher: Kadokawa Shoten
Genres: Adventure, Fantasy
13. So I'm a Spider, So What?
Published: 22 December 2015
Publisher: Kadokawa Shoten
Genres: Action, Adventure, Comedy, Fantasy, Reincarnation
12. The Devil is a Part-Timer!
Published: 27 December 2011
Publisher: ASCII Media Works
Genres: Comedy, Fantasy, Romance, Supernatural
11. Restaurant to Another World
Published: 18 November 2016
Publisher: Square Enix
Genres: Comedy, Fantasy, Gourmet, Mystery
10. Arifureta: From Commonplace to World's Strongest
Published: 6 February 2016
Publisher: Overlap
Genres: Action, Adventure, Fantasy
9. Wise Man's Grandchild
Published: 1 March 2016
Publisher: Kadokawa Shoten
Genres: Action, Comedy, Fantasy, Reincarnation
8. Akuyaku Reijou wa Ringoku no Outaishi ni Dekiai sareru
Published: 5 December 2017
Publisher: Kadokawa Shoten
Genres: Fantasy, Romance, Shoujo
7. Re:ZERO -Starting Life in Another World-
Published: 27 June 2014
Publisher: Media Factory
Genres: Drama, Fantasy, Suspense, Psychological
6. Isekai Izakaya "Nobu"
Published: 4 July 2015
Publisher: Kadokawa Shoten
Genres: Comedy, Fantasy, Seinen, Gourmet
5. Konosuba
Published: 9 September 2014
Publisher: Fujimi Shobo
Genres: Adventure, Comedy, Fantasy, Parody, Reincarnation
4. The Saga of Tanya the Evil 
Published: 26 April 2016
Publisher: Kadokawa Shoten
Genres: Military, Reincarnation
3. The Rising of the Shield Hero
Published: 5 February 2014
Publisher: Media Factory
Genres: Drama, Fantasy
2. Overlord
Published: 26 November 2014
Publisher: Kadokawa Shoten
Genres: Action, Comedy, Fantasy, Supernatural
1. That Time I Got Reincarnated as a Slime
Published: 26 March 2015
Publisher: Kodansha
Genres: Reincarnation, Fantasy
Recommendation: Best Action Fantasy Anime Series
Source: Rank-1 Media
