killing off a character doesn't make your work good automatically, it should be a logical consequence of the plot, and not simply being done for shock value.
I totally agree with you on that . And I never said otherwise
If you want me to recommend some manga I need to know at least what kind of manga you like? Killing "MCs" is a bit vague as point reference, it can be done at various scale in number and in time. Even the definition of the MCs in a story can be done at various range by the author and by the reader, Game Of Thrones is a good example for that.
Only taking in consideration the "importance" of the deaths/deads and number, Claymore, Vinland Saga or Kamisama No Iiutoru could be good examples if you want to compare to GoT on that point.
As for comparing manga/light novel authors to "actual" novelist that's not really the point. You can objectively say someone, being a novelist or mangaka/manhwaga, is a great author in terms of story telling or narration. However I don't think you can compare skill or quality here, being a mangaka or a novelist take different skills and both works have different kind of publication or work environment. It's the same as comparing a picture and a painting or a photograph and a painter for me.
I'm what you can call a "voracious reader" and even if I love french/english literature I wouldn't dare say authors such as Kazuo Koike, Takehiko Inoue or Naoki Urasawa aren't as good or skilled in their genre than some classic authors. But it would be pointless and subjective to compare them.