I've read a few here's a list of them with things I did and didn't like:
Gekizumi Dungeon Desu ga "Skill: Hanshoku" de Gyakuten Shitai to Omoimasu
There's sexual violence in it which I didn't enjoy. The main character doesn't have morals and in a general sense it's depressing.
Astro King - Shoukan Yuusha dakedo Maid Harem wo Tsukurimasu!
There's so much sexual violence and lack of morality in the setting that I wanted to puke. However they did give a few of the female characters distinctive personalities and well written back stories that made me want to get to know them. However it didn't have much if any romance between the main character and them. This made most of the scenes where he 'got with them' so to speak feel transactional or sad
Warrior Princess Survival Saga: The Unsanctioned Intergender Relations on a Deserted Island, Battling for the Fate of Another World
They have a main female character be a loli which simply made me not want to read past the first chapter but I did. They fleshed out the characters decently and they have the main character a decent enough backstory where he's a correctional officer at a school which was interesting. However the writer decided to give scenes that tease sex which made me more uncomfortable then them just doing it and skipping past it. They gave some of the characters interesting traits or tropes such as a side character dragon being tomboyish or just a brute which was more interesting than just having a calm and composed female side character that did almost nothing except explain the world as if the main character was dumb. Another annoying thing is that they're all on a normal island and not in a fantasy world which that a long with a lot of other things made me drop it.
I've also watched Mushoku Tensei which I didn't like due to the main characters actions throughout the entire show. However I bring it up because it does a lot of good things throughout it such as giving all of the female characters backstories and reasons to like them. It also does some amazing world building that I ended up liking. They also give some reasons why the main character has a harem Instead of just throwing it into the story. It also shows characters not liking it and others being okay with it and giving reasons why or why not. There's also a lot of flaws such as the main character getting with his cousin (eris). Sexualizing underage characters which made me uncomfortable to say the least and did a lot of other things wrong that I don't want to get into.
There's also welcome to demon school iruma-kun which is a fantasy where I think a few different people like the mc. It's not super erotic or anything like that but I'd consider it almost perfect with how it portrays female characters and the world they're in.
hmm...
Your examples are mostly fantasy/isekai. What about harem stories you've enjoyed so far? What are they?
I don't read Iruma-kun. So I have nothing to say about that one.
I dropped the first 2 after ~5 chapters with score 3 and 2 out of 10. So, nothing more to say.
I like the middle two, but I never considered them as harem stories.
We know that there will be harem in Mushoku, and we can safely predict the high possibility of it in Princess Survival Saga, but I've never read them for the harem story. To me, the harem there is not the part that is being pursued by the story.
So I don't actually consider them as harem "romance" story. I don't read them for the harem.
(I read/watch Mushoku for the isekai action fantasy, I read Princess Survival for the comedy)
If it's something like Isekai Yurutto Survival in place of the Princess Survival, then yes. I consider that one as having harem "romance" elements that are pursued throughout the story. But you said you don't like the "normal island".
Ok, I've mentioned Isekai Nonbiri Nouka, because that story is basically the MC's everyday harem life.
How about Risou no Himo Seikatsu? The harem romance there is quite slow and gradually developed throughout the story.
7-nin no Nemurihime is a fun harem romcom.
Other isekai story with decent harem "romance"... I guess... Genjitsu Shugi Yusha and Hachinan tte?
They're not particularly good imo, but they're alright. At least the "falling in love" part isn't done in just 1 or 2 chapters.
Not harem for the sake of harem. (tho, Genjitsu kinda fell into that trope in the latest chapters)
of, there's also Isekai Kenkokuki
(I only listed those that did not have sexual depictions in the story)