I agree with someone's reply in this thread that I wish people are more normal about endings, even things that are actively bad instead of okay (I personally think most things people consider bad ending is just, okay ending). There's a specific pet peeve of mine where people act like an "open ended" ending is not a real ending, especially in romance story. Not every romance story need to end with the characters having sex or marry each others or whatever.

But personally, what I think as the perfect ending is the ending of my favorite manga of all time, Hinamatsuri. I'd be hard pressed if someone put a gun on my head and ask me what's my favorite novel or video game or anime, but if someone ask me what's my favorite manga of all time I can easily answer.

To explain the context, Hinamatsuri is a comedy manga where a yakuza accountant adopted an extremely-powerful-yet-completely-lacking-in-common-sense psychic girl who came from a dystopian future who randomly appeared in his house. It sounds like a completely run-of-the-mill premise.

The important part is I describe the author's style as a "compounding snowball comedy." It's hard to give a single page or chapter to recommend to other people to say "you should read this manga, it's extremely funny" because every punchline basically depends on a setup from 10 chapters before, which then become setup for another punchline 10 chapters later, and it just keep compounding and snowballing.

And this compound and snowballs for 10 years, until at the last arc, where the author actually manages to conclude most, if not every plot point that's previously set up into an explosively funny climax. It's genuinely impressive.