I'm reading Domestic Girlfriend and am writhing in my chair every time some new, interesting, adorable girl shows up but MC ultimately decides "you're cool and all but I'm gonna keep dating my sister".
Fair enough, that's the story. But I would love something where new girl wins for once.
Not necessarily the *best* ending, but at least pretty good and that's arrived at naturally.
My pet peeve in romcoms is that moment when you can feel the author crack their knuckles and go "whelp, time to wrap this shit up" and suddenly they're resolving all the plot threads as quickly as possible. Kaguya-sama and Nisekoi are great, actual endings themselves are great, but their shifts into Ending Mode in the last (manga) arcs are so abrupt that it breaks my immersion.
Examples of endings with the vibe (all manga but would take anime suggestions):