I'm gonna say story. Art is just as important, but as I've said it a million times before, people will come for the art, but stay for the story. It doesn't matter how beautiful your comic is, if the plot/content sucks, no one's gonna want to stick around for it. That's one of the biggest reasons why comics like Cyanide and Happiness, XKCD, and Homestuck are so popular - the content they deliver is worth reading. If they looked beautiful, well, good on that, but if the content they made wasn't as good as what they're making now, then what would have been beautiful art would have just been overlooked.
Honestly, there's no conflict between them. In comics, the writing and the art both tell the story. Do you know how much story you can tell with a single panel of a character's facial expression? Or how much meaning you can pack into the contrast between what is said in the dialogue and what is shown in the pictures? I mean, my story would be nothing without the visuals.
And as my ambition is to be good at storytelling, I strive to be good at both aspects.
I think both are very important and everyone will have their own preference. However, me personally, I care a little more about the story.
hands down writing is more important. good art is always important, and can really sell a comic, but it comes down to the writing.
there are loads of comics sold professionally with, honestly, bloody awful art that get sold on their awesome storyline (im thinking mainly of runaways here)
in western comics especially, you tend to get a 'good art but bland story' or 'bland art but good story' kinda thing, although there are more and more exceptions these days, lets not forget they do hire artists separate from writers, which makes getting both good art and story easier.
its possible to make a successful comic where theres little to no story but tonnes of incredible art (and probably a fair amount of fanservice /sigh) but honestly id take stick figured with a good story over fancy art with nothing behind it any day.
It's important to distinguish the writing from the story. The writing and the art are used to tell the story. I don't think it's a case of one versus the other - Providing they both compliment the story, they can be any any style or quality (or even absent?).
I'm keen on word play an writing style and my webcomic is mostly a single repetitive image with very little variation. In honour of this thread I have written a strip with little text and a different image in each panel. Enjoy1.
If the writing's bad, and the art's amazing, I'm not going to read it. If the writing's amazing, I don't care how bad the art is ^^
Hehe for both versions of your questions, its still 50/50. I try to improve both to better tell the story
well,comics is telling the story through the art of illustrating
the art and writing should compliment each other,I think
peeps shouldnt prioritize one over the other( as much as possible)
I would say writing, probably. When I think of it from the viewpoint of being in a writer-artist duo relationship, it's much easier for me to see myself in the shoes of the scripter than the one drawing.
Additionally, I'm more confident in my ideas and my ability to refine them than I am in my ability to draw out ideas and refine those drawings.
When it comes to my personal preference, both are equally important. When it comes to making a successful webcomic though, it's all about the art. Comics with good art will attract attention even if the story is crap. It's not because I think people are shallow-minded or anything negative like that, but it's simply the delivery of the medium being visual.
The art can be judged in a few seconds just by looking at it, but you have to read for a while to judge the story. You can see a banner and immediately, if it has bad art, you won't click on it. But if you see a banner ad that has really good art, you will click on it, and you will read a few pages at least before you decide if you want to continue, or it's not worth reading.
Writing is also more universal, in that everyone thinks that they are good at it. If you have vivid imagination and a word processor, you probably think you are good at writing. With so many "good writers" in the world, it can be difficult to find perspective on where you stand, to evaluate yourself, or to stand out from the crowd. Especially with some of the absolute garbage that ends up banking millions in popular media, while amazing works remain obscure. It's really a crapshoot.
I find it's also easier to see clear forward progress with art. An artist can improve page-to-page and you can immediately see the results. Where as with writing, you may have to wait for years to see if a long-form comic's story ever goes anywhere.
I enjoy art and writing equally, but I never feel like I'm good or bad at either thing. More like, I'll look back on something I did before, and I'll see a few things I did well, but a lot of stuff I could have done better.
To me, they're both important. No matter how good the story is, if the art is terrible, I won't be able to focus on the story. A comic is a visual medium, not a book. I strive to improve on both aspects!
There is more truth in this than I like. I have seen some absolute crap comics at the top of the various webcomic lists, only because the art is pretty. Honestly, the reason I still read so many published comics is because while it's easy to find pro-level artists in webcomics, pro-level writers are few and far between. And the absolute worst part is what you pointed out later in your post, people think they are good at writing, and have never studied the craft.
Eagle
(But I think that's going to change)
Both... There is a saying that people will welcome you by looking at your clothes, but will send you away by looking at your brain (or heart). It means that art is important to sell your content. I have a favourite comic here on Tapastic which is not very popular - but the only reason it is not is because the art is not still so appealing so somehow it stays unnoticed. So if you can jump the barrier of first impression, you may find a lot of gold. But art is important in comics because it is the tool that tells the story. So if you want to tell it in a good way, you should improve both. At the same time art is not enough for comics as well. It will totally be just an empty shell if you don't have a good content to fill it with 
Well, I work as an illustrator so I guess it's quite clear which option did I choose XD But both are really, really important. It's the essence of comics! To unite art and writing into a good, new art form. If one of them is bad, the whole thing comes out wrong - maybe because it's awful to look at, or maybe because the story is boring.
I wouldn't mind to be a better writer, though. I have toyed with the idea of writing some short stories, but never actually got to it... someday, someday. At least I can get better with comic scripts, and that is enough for me at the moment ^^
The visuals matter. Sequential art does not require a story to exist. A series of panel with a ball rolling in is a comic. I also dislike the whole pretentious graphic novel thing. Comics are not novels. They are sequential illustrations. The progression from one panel to another is all that matters. If you want to tack on a story or some other experience, sure, it's quite feasible. But let's not fool ourselves thinking that the story matters. If it did, we would be reading novels, not looking at pictures.
Once all pretension to being a novelists are gone, that's when what is known as storytelling can occur. Storytelling is the art of using visuals to tell a story. Notice that I didn't say, the art of using words to tell a story. In comics - the one where the cartoonist gets it at least, the visual tell the story as much as possible and words or "writing" is subservient to effective storytelling.
The writing for me is more like a conceptual thing. The big idea. But the nitty and gritty is all storytelling. Only after having read a good chunk of a story does the big picture often starts to show its tail.
I know that most will disagree with me but it has been my experience and how the greats in comics that I have studied have handled their work. They never pretended to be novelists or writers. They were cartoonists and that was good enough for what they were doing.
They also were not ashamed of calling their work comics, as opposed to using grandiose terms such as graphic novel. I really dislike this term. 