Just like many have said, there has to be a balance to both art and story.
There's a saying here on Tapastic and a lot of other place all over the comic world:
"People arrive for the art, but stay for the story."
(or other paraphrases of that same statement, but I like this version because of the alliteration involved)
Simply, it means the visuals will pull in potential readers, but if you have a lousy story, you will not be able to find a core audience.
However there are some exceptions to the rule, one I believe is Homestuck, a webcomic series that has become a cult hit and has an enormous fanbase. I've watched a bit of it on Youtube (someone reading it aloud) and was fascinated by the story, while the art itself was more passable.
Another, more known exception to me is Attack on Titan. If you have read the manga, the story and drama is good, but the art sometimes is a bit... under the par for most shonen types. But then again, the artist knows what he wants to do and is able to do it, but sometimes, I find that the proportions are a bit off during certain moments. Then you look at the anime. Holy crap it's above most? It looks incredible. I mean look at that opening! Then you look at the manga again... wut.
And I know there are comics out there that get away with good art but little to no story involved. I just don't know any on the tip of my tongue.