Gwenpool will never not be my favourite isekai story ever. She gets yoinked from her universe and is plopped into (one of) the marvel universes and just. God I love seeing her do what she does.
I think a small part of why I like her so much (which is something I dislike about a lot of other isekais) is that she isn't in fantasy land #122 or some game or whatever. It makes the places she goes a lot more visually interesting. But that's really only a thing in relation to other isekais. It's a bit like what spider-verse did with stories set in New York. Miles doesn't just live in New York, he's a kid from Brooklyn. And he doesn't just go to a high-school from New York, he goes to Visions Academy in Manhattan.
I can understand though (if only a little) why fantasy is the go-to genre of most isekais. It'd be difficult to be someone of significance in a world that has something different going on without a lil somethin somethin from a god or whatever (although that does sound like a really fun challenge, writers feel free). It'd be really hard for anyone without some insane street-smarts to survive in a place like Night City, where a god would make no sense. The only thing that makes Gwen a person of significance in her stories, besides her 4th wall breaking abilities, is her status as a main character
The biggest thing I like about Gwenpool's stories, which I recognize is a symptom of being part of a larger universe, is that Gwen will not, and cannot be at the center of anything that isn't her own stories. A lot of other isekai protagonists, as is often the case when their power is given by a god, have a tendency to feel like the only interesting things about the story must involve them in some way.
One of my favourite moments in her stories is when she gets in a tussle with Deadpool, and he gives her a lot of shit saying it's stupid to think that she's invulnerable just because she's the protagonist in this story (which is kind of dumb Wade, cuz while that statement does work in say, a Punisher or a darker Wolverine storyline, this is neither of those + its in a clean, anime-esq art style). He continues giving her shit saying that she's never gonna beat him, a character with hundreds of comic issues, several games, a handful of animated appearances, and two live action movies. And the shittiest of all, that most people would think she's a Gwen Stacy variant.
Which is mostly to say that her biggest weakness is characters that are more popular than her, which is inherently an effect of her true greatest frenemy: Marvel Editorial.
My second favorite isekai is GATE: Thus the JSDF fought there. But only cuz I had so much fun watching medieval armies get their teeth kicked in by outdated cold war weapons
GATE: Thus The JSDF Fought There was okay, but it could have had a better opponent for the JSDF.
Now, don't get me wrong, seeing a modern military curbstomp Generic Magical Rome #34534 can be grimly entertaining. But Gate's best fights and best conflicts are the ones where the JSDF technical advantage doesn't give them a hand up. A similar portal fantasy, 1632, which sent a West Virginia coal-mining town to 1632 Germany, had similar writing problems and solutions.
I think a peer conflict portal fantasy would have been a better JSDF-driven war story.
So what's on the other side of the Gate?
Throne, The Red City, The Center of The Omniverse, The Tower Within The Wheel, from Kill Six Billion Demons.