I speculate that there might be some sort of spectrum of the honorifics to use for manga-ka/anime directors.
For example, I think one might be able to get away with addressing younger, and more, for lack of a better word, lively, producers like Yamada-kun and the Seven Witches' Miki Yoshikawa and Hiro Mashima with -san. However, I feel that -san doesn't do justice for people like Hayao Miyazaki or Akira Toriyama, who created works that many of us regard as classics or masterpieces that have influenced other manga-ka/anime producers very heavily. And then there are people I feel lie in between the two bounds like Eiichiro Oda and Masashi Kishimoto, who are in their own right, very successful, but can't be cited for nearly as much influence as the aforementioned two.
That being said, under what Japanese honorific should manga/anime fans address manga-ka/anime directors?