What manga/manhwa/manhua that you have read you feel is better than the source(novel) Imo "the distinguished cute master" manhua is better than the novel. Granted most details from novels are gone when adapted to manga or anime, but her chibi artstyle is to live and die for. Yes, yes really
Who Made me a Princess. I heard the novel barely touched on Claude and made the cousin more distant. In the manhwa, Athanasia's relationship with him is the heart of the series.
Does soulland 2 count? I started it before the novel and the art was impressive imo. I did finish the novel because it looked as if the manhua was dropped.
Not exactly what you're asking, but the Madoka Magica Novelization felt better than the anime to me~ And I gotta say, I really really really looooove the anime. But the novel felt even better to me~ ... It's rare to find adaptations that are better than the source though. ... Maybe music-related animes that are based on music-related mangas? I mean... The anime will have songs in it, so it can explore the musical aspects a lot better than the manga can~ But as for mangas/webtoons that are better than the source... I'm not sure I can think of any for sure... If anything, I remember reading a handful of chapters of a Korean Novel and thinking it was really meh, but the webtoon adaptation was really lovely... I don't remember its name anymore though, but it kinda made me stop wanting to read Korean Novels and instead only focus on the webtoon adaptations instead.