This is actually such a complex question omg.. I am answering in reference to rofans but this can be equally applied to all manhwa

1. Visuals.
Im shallow like that fr, but not only the quality of the art but if the character design/fashion is good or thematic I always get a bit giddy, what makes stuff more memorable is when it perfectly manages to capture a very specific vibe that only good creative direction could manage. This also includes matters of personal preference like brown haired mls 😼👍
- Examples with distinct visuals/vibes include, Spark in ur eyes, How to Survive as a maid in a horror game, Regina Rena, Where the shooting star falls, Your eternal lies, Suhee0, Morgana & Oz, Jungle Juice etc etc

2. Things have to connect
I actually don't care about realism and I really hate the idea that a good story is one with "no hero/villain", i think this a reductive judgement for art. Rather, that characters can be as they like, as long as writers don't skimp on making solid explanations for why a character does what they do. Not only this, but a character shouldn't just be explained but integrated into the story, their actions should impact other actions - and other characters should thus exist within the periphery of that impact whether direct or indirect or completely by the theme or morale - I hate a character that will have sufficient explanation but little weight to how it matters in the story. A good example of this is Daily Jojo

3. Setting integration
A stellar story for me is when the setting adapts/integrates with the character/s and the setting doesn't simply exist as a static background for the characters to interact with - in fact, I dislike when any art analysis/metacommentary hyper-emphasises the role of the living as an occupant of the seemingly inanimate, a roFAN shouldn't ever just be a setting - when u sign up for fantasy, you're signing up for the setting too. Sometimes I don't mind the nonsense of an isekai rofan that barely implements the genre into the story, but what really frustrates me is when authors create loopholes that could have simply not been made had they just decided to not make it an isekai. It's so frustrating, because it could have been a perfectly solid story had they at least known their bounds as a writer - it's one thing to decide to be a bit silly and random but it's another to be so silly and random you leave the story feeling like there was a mistake.

4. Things have to loop
I also like when the full story loops back, things that have happened before should be explained at the end - even better if it is explained by the driving force of the author/artist to push the audience into the exact emotional levity required to make "redemption" appropriate for certain characters, which is why i despise most redemption stories, people take it too lightly for what is usually quite serious subject matter, and the question of redemption should never be simply that of redemption but a collection of instances, situations, feelings, emotions, redemption is a an unending process that never cuts clean. What also frustrates me is making the protagonist the sole arbitrator for telling us who & when someone is "good/bad", i don't like when the story stops at the character, as I said the setting needs to have a life of it's own and authors need to at least hint that other characters have a life outside of the protagonist, so when a character is made - but not followed up on bc they did their "job", the loop is essentially broken for me.

5. Stories need to end when they end
I hate stories that drag. Lots of seinens make this mistake but a lot of manhwa really does just drag for the sake of dragging and totally ruins the novelty of the story, it's like "what filler episode am i getting this week?", it's so frustrating. Also, lots of stories don't SET out to offer any promise for us stick around, so it feels like it's dragging when you're barely a few chapters in, bc the author failed to set the scene from the get go, as the relationship w the author/audience is almost a push and pull to maintain enticement. This is for sure a personal preference, but starting a rofan with "once upon a time" gets VERY tiring VERY quickly because you know you're up for a lore dump and I am not a lore lover, ik i said I prefer when they mean fantasy but that was just an example - I hate stuff that goes too hard on fantasy to the point it's basically a sci fi where you have to learn all this politics and lore and worldbuilding and you're flipping through a trillion lore dumps that the author for some reason thinks I'm going to remember?? Once with "kill a villainess" i just skipped all the lore and the story still went rlly hard, like I didn't really NEED to know all that and since i hate knowing about all that I will skip it if it's boring asf.

6. Characters/Side characters
I referred to this at the end of point 4, but I always really hate a rofan with a maid character that is the very conception of loyalty, it really pisses me off, bc to what end do they have that loyalty? There are too many questions unanswered for a character usually SO important to the protagonists success/emotional needs/story etc. and yet they themselves are barely explored outside of their undying obsession for the FL's success. Occasionally the maid/butler will take care of a family that might kick off an arc for the fl/ml to demonstrate their kindness and re-remind the audience why the maid/butler is just sooo dedicated - but that's far from enough, bc that side character still exists AROUND the protagonist and that incident usually just serves to explain the dynamic with the protagonist - had it been another character, the story would be no different. Integrating things outside of the good ole "she saved me & I owe her with my life QQ" narrative is so frustrating to see time and time again because no human being lays out their life that quickly. It makes me question the author's perception of human rights, like a character who is just that obsessed with fl/ml can get kind of questionable - does this character, exist, outside of being the "good" one?? A really good example of a faithful maid explored well is in "Tears of a Jester" which captures one of my alltime favourite rofan scenes, where the maid converses w what is her "enemy" to almost reflect on the way this maid's humanity hinges on her faithfulness to a young girl that is suffering from the story, this not only says a TON about the maid, but it says a lot about who she is caring for, what her personality is like and to what extent she willl fight for it & why, I also see reference to the setting - in that just bc she wants to do it, makes it no less her duty - but the fact she will go further, is literally just her duty as a good person to protect the weak and young. I'm fr not asking for much, "the portrait" covers this really fuckin well esp with the servants of the duke, and even that one sort of has pitfalls with making side characters suspiciously loyal - dont even get me started on the way they worshipped the duke - and yet I really enjoyed the way everything was employed bc the writer worked their darnedest to make these characters have lives of their own and not of ones that revolve the fl/ml. (Special mentions: I hate when stories depict side characters as strong & supposed to protect and they don't protect just so the ML can do that it's so grrrr - I also hate the maid trope of the maid constantly bitching about the fl being adventurous or whatever, gets so tiring coz honestly there'd be more there to say ab how the maid would likely be punished if the lady randomly disappeared from the manor like bffr)

6.5. Socio Politics
Following on from point 6, if you make a character in a place of power - don't forget they're in a place of power - and while a good story can be a good story, for sure, there is always potential in a story that doesn't ignore power dynamics & the moment a writer takes a step back to re-analyse the sociopolitical dynamics of each character outside of their "good will", we see so much more to be said and done about how legitimate their personalities actually ARE and what their actions truly mean within that context. Don't pretend the servants are loyal to the fl/ml at their own expense when that is their literal livelihood, don't pretend the money the duke has is fair and good money, don't pretend the lady can be totally benevolent when she has clothes worth more than a servant's yearly salary, don't pretend a king/queen has a "good and proper vision for the future" when they js so happened to care about poor people a bit more than the avg noble, so many rofans just sound like silly propaganda sometimes, and you can tell when you see the type of depictions they have of CERTAIN groups of people. Anyways! A GREAT example of this is "wall of glass" where the characters relationships hinge on their socioeconomic class & the major divets n the story & characters personalities in that world are dependent on that dynamic, in the example of Edward, when he eventually becomes rich enough, he reflects on the unethical standards of the rich people he used to serve to shape his interactions with his own servants & major conflicts with himself and his close ones. While I'm not a huge fan of the Edward being "New bourgeois" from a rlly objective standpoint, we still get a reflection on why 1. his status is a good thing in this specific period 2. that his position is not one of butterfly and rainbows for sure

Anyways yeah i rlly hope you enjoyed, love u ella ;3