What is your best isekai anime?

Overall, probably Slime Isekai. It's got a good mix of wholesomeness, action, comedy, and world building. And it has just the right amount of OP in the MC.

Overlord is a good runner up. Great character development, good story and humor, intriguing world, etc.

Mushoku is easy top 5 but the bullying and horny drop it down a few notches for me.

Konosuba is also top 5. It nails the parody.

For non-anime, Reincarnated as a Sword is my favorite isekai light novel series, not that I've read all that many isekai light novels. However the anime adaptation was mediocre at best. It barely touches on the deep world creation and character development found in the LN.

For video game isekai, Shangri-La Frontier. No trapped in a video game nonsense. No completely unrealistic game mechanics. The game feels like it could be a real game. And the MC is OP only in the sense that they're good at games, not because of cheats.

Villainess isekai is practically it's own thing now and I have my favorites there as well but the classic is All Routes Lead to Doom.

I really love isekai so I could keep going but I'll stop here before I start talking about Trapped in a Dating Sim.

Every one you mentioned is great! I really enjoy all of the villainess isekai, and Trapped in a Dating Sim is really a hilarious variation that came early in the dating sim sub genre. I love it when the main character is a villain.
- Ngl, the Trapped in a Dating Sim anime is what got me reading more light novels. The anime wasn't perfect by any means, but it was still so good. I wanted more of that world and the light novels didn't disappoint.

tensei shittara slime datta ken

Konosuba

Being a parody, it subverts most tropes of isekai anime. Its humor is exactly my type too.

Honorable mentions:

Most other isekai anime have the same cookie-cutter plot, making them so predictable and boring. Or they have an interesting premise, but waste it with poor writing and dumb characters.

uhh... spirited away?

mushoku is up there if we are talking about the modern kind of isekai

I never thought of Spirited Away that way but now that you mention it, it does resemble isekai.

Re:ZERO or Ascendance of a Bookworm (underrated in my opinion).

Ascendance of a Bookworm is a favorite of my wife and I. We've rewatched it a few times, as it has a cozy feel to it sometimes. I really hope they continue the story but it is at a decent enough stopping point if doesn't get any more seasons.
- The next season was announced in December of 2023 and it’s changing studio to Wit Studio, so hopefully they do a good job of it. I’ve rewatched it and it’s great for being both relaxing and engaging at the same time, planning to read the light novel at some point.
Ascendance of a Bookworm is amazing. I really hope it gets some more seasons soon.

Mushoku is probably the best by such a large margin i couldn't think anyone answering different was serious. Log horizon is probably the only isekai that's done the modern game junk well.

My biggest problem with Mushoku, and why I feel like I literally cannot recommend it, is because of the weird pedo stuff. It would be fine and easy to forget I guess if the show stayed in fantasy mode, but for whatever reason any time there is something slightly sexual the show writers decide to remind the viewer "erm actually the main character is a 40+ year old man." That just pulls me right out of the show.

The other parts are cool, but that one thing really stops me from enjoying it more.

.hack//SIGN

without it we wouldn't have many of the isekai animes as we currently do

Truth.

Konosuba Since it's a parody.

I don't like isekai.

Visions of Escaflowne was pretty great. It had basically everything, a fantasy world, giant mecha and a Yoko Kanno soundtrack.

Feels weird to say that one of my favorite isekai is a shoujo mech anime, but you're absolutely right.

Heck, I might even be able to say that two of my favorite isekai are shoujo mech anime depending on how much I like Magic Knight Rayearth once I finally get around to watching or reading that.

I like Overlord. Its got good worldbuilding but it also doesn't always take itself too seriously and throws in some comedy every now and then to keep it lively.

I also really liked Knight's & Magic. There are not enough medieval fantasy / mecha hybrid shows out there, despite anime being the perfect medium for it.

Skeleton in Another World was a fun one once you get past the first episode. The attempted rape scene right in the beginning just shows too much on screen IMO, it would have been better to cut some of it short and show the scenery around more rather than what was actually shown. Very uncomfortable, which I hope is what its supposed to make the viewer feel, but then literally none of the rest of the show is every that intensity. Like it was almost Perfect Blue levels of showing too much for too long.

Reincarnated as a vending machine, I now wander the dungeon is my latest favorite. It's funny and a cute show.

My favorite isekai is Farscape.

But if it has to be anime: Inuyasha.

So many isekais have great starts, but fall off execution in the second season. Maybe they run out of ideas, or just had a good concept, but then lacked creativity to keep the plot interesting... So there are a lot of S1's

Sword Art Online Season 1

Log Horizon Season 1

Level 99 Villainess

Shangri-La Frontier

Rising Of The Shield Hero Season 1

Overlord

I liked Grimgar a lot.

It has unique visuals, but what really sets it apart is the great - what do I even call it - significance through realism? It has a lot of depth and is very different. It has my definite recommendation too.
- I wish we had more Grimgar.
  
  Like most I'm already tired of the over the top plot of most fantasy stories, I just want the shenanigans.
  
  I really want Frieren but with a permanent base and more adventurer politics.
  
  I guess there's Goblin Slayer but IMO their character especially the supporting one isn't as developed.

Konosuba

Re:Zero, Konosuba, Overworld, and That Time I Got Reincarnated as a Slime are some of the best, alongside SAO which started the modern version of the genre.

Digimon & Inuyasha

I'll let you guess from my instance 😁

Ascendance of a Bookworm. A really good one!

Permanently Deleted

Space Jam.

Honest answer, much like typical shonen series I find isekai really boring and hard to watch. If I see "reincarnated" or "another world" in a show's title it's pretty much an instant pass from me.

Give me more DanDaDan dubs pls.

Personal Favourites which haven’t been mentioned as much

Tuskimichi Moonlit Fantasy
Ascendance of a Bookworm
No Game No Life
In the Land of Leadale
So I’m a Spider So What
Didn't I say to make my Abilities Average
Death March to a Parallel World Rhapsody

Cute / Fluffy

Ascendance of a Bookworm
In the Land of Leadale
Kuma Kuma Kuma Bear
The Weakest Tamers Journey To Pick Up Trash

Action

Tsukimichi Moonlit Fantasy
Rising of the Shield Hero
Reincarnated as a Slime

Politics / Kingdom Building

Log Horizon
Reincarnated as a Slime
How a realist hero rebuilt a kingdom

War / Fighting

Overlord
Saga of Tanya the Evil

Comedy

Konosuba
Didn't I say to make my Abilities Average
So I’m a Spider So What
Reincarnated as a Vending Machine

Struggle and Strife

re: Zero
Jobless Reincarnation
Rising of the Shield Hero

Game Worlds

No Game No Life
Log Horizon
In the Land of Leadale
Kuma Kuma Kuma Bear
Overlord
Rising of the Shield Hero

Gender Bender Characters

She Professed Herself Pupil of The Wise Man
Life with an ordinary guy who reincarnated into a total fantasy knockout
Log Horizon
So I’m a Spider So What

I really liked Uncle from another world too, but I wouldn't list it to that question. I guess because it's more of a comedy than with a spanning story and depth or development.

Scrolling through the comments to remember some of them,

Mushoku Tensei - great - the first two seasons have exceptional world building, story telling, contrasting, and developments; not everything is great, but a lot is; for me, last two seasons fell off a bit
Grimgar - very good - very unique, great world and characters and relationship between them
Ascendance of a Bookworm - very good
The Eminence in Shadow - very good - exceptional satire
The Magical Revolution of the Reincarnated Princess and the Genius Young Lady - very good until the ending, with exceptional visuals and vibrancy
Life with an Ordinary Guy Who Reincarnated into a Total Fantasy Knockout - very good - great comedy with a gender bend/swap

/edit: Found two more from my list of good/decent non-harem isekais I replied to some no longer existing lemmy post.

Unrelated to isekai, but I saw from your site that you migrated from Wordpress to Hugo. What method did you use to do that? I have an old wordpress site that I keep running for somebody, but it isn't actively updated anymore. If I could convert that to static html and host it using something like github pages, that would be awesome. I looked into it once before, but there were a bunch of different plugins and methods, so the inertia of not doing it won out.
- too much detail; leading up to the findings that follow
  
  Looking at the git lot, it looks like it was in 2018. I don't remember, and it's not documented that thoroughly in the commit messages log. Looks like I had content pages in Joomla, and the blog in Wordpress.
  
  I may have exported the content via a plugin, or separate tool that reads from the database, did exported from the DB myself. I certainly did some mass-fixups via text search and replace. (I can recommend VS Code for that.)
  
  Unfortunately, I had other projects that I migrated, so I can't remember which one I did what. :)
  
  Now that I know the date, this is the migration blog post
  
  I used content exporters to export the Joomla pages and Wordpress pages and blog posts into markdown content files for hugo.
  
  Unfortunately, it's not more specific than "content exporter into markdown". But who knows if those specific ones would still be available today. :)
  
  So I would suggest to use any Markdown exporter that's available now.

At risk of showing my age, The Twelve Kingdoms blows most modern isekai out of the water, even with its flaws. The MC‘s journey and character growth is amazing, and the world building is incredibly unique.