Some interesting thoughts on this and what's more intriguing is that, for me, the novel versus comic/graphic novel brings in some huge differences in order.
Novel -- story first and foremost. Some of my favourite works have vague or constantly transforming characters that are carriers of the plot and not much more. Also, first-person narratives can often work to obfuscate the division between author, reader, and character, melding the three to create a piece that harmonises on memories, firsthand experiences. So with respect to my preferences, by extension, character isn't very important for an immersive story in novel format. The more abstract and crafty the approach of a story, the better.
Comic format -- art, characters, and story. Especially if it's a one-person operation, I find that if a lot of attention is given to the art, it speaks volumes of the passion even in a vague concept. Characters can be brought to life with an imagination that inserts itself. It's not to forgive inept writing or badly constructed characters, but personally, I can work to make connections in a loosely laced story if the art is highly appealing. It certainly doesn't guarantee success on a large scale (my favourite books and films have made my friends distrust my opinion on quality, OOPS).