I’ve been reading a number of comics-slash-graphic novels, and too many of them are trying to do in comic form what word-only forms (novels, essays) do better. There’s really no point to a graphic story in which the visual element isn't pulling a heavy load of meaning and mood. Too often you have art that isn't doing a lot except, perhaps, to conceal how drearily familiar the story is.
But a fine example of art that contributes mightily to the character and power of the storyis Asterios Polyp, which would be a fantastic book were it not marred by an utterly ridiculous ending. I get annoyed every time I think about it. But until that ending, the book is a great example of visual storytelling.