Sorry, but that is the real answer to what makes a good comic. You can have the prettiest artwork in the world - if your writing is shit, it's a bad comic. You can have the best writing in the world - if your artwork doesn't communicate it properly, it's a bad comic.
(and before someone yells "XKCD!" at me, I think XKCD's artwork communicates perfectly well and Randall Munroe has found a way to be expressive through stick-figures in a way that works really, really well for him).
... also, is the question here "what makes a good comic?", or "what's important to make people click on the link to my comic?" - because those are two very different questions.
If the query is "what gets the most immediate attention?", then the answer is obviously artwork. Humans are very visual creatures (thank you, evolution), so good, fancy, probably colourful artwork is obviously going to get the most immediate response, and readers who click that link might be more likely to stick around for a bit even if the writing is terrible.
However, if your writing is sub-par, you are very likely to eventually lose those readers. You can hook a reader on cool artwork, but if your writing falters, they will lose interest. We read comics because we like stories, right? And if you aren't telling a good story, it kind of falls apart.
And btw, the heavy lifting of storytelling isn't entirely on the written word, here; comics tell stories through visuals; facial expressions, panel layouts, colour coding, etc.
It doesn't really even need to be a case of beautiful art+terrible artwork either - I read a comic yesterday that had beautiful art and perfectly passable writing - but it was a story that entirely failed to hook me. It was just okay, with nothing in particular that made me want to pick up the next volume; I wasn't concerned about what happened next for all the characters. It's a comic that might work for others, but did absolutely nothing for me.
Hooking someone into reading your comic is, at best, half the battle; the other half is engaging them in the story well enough to keep them coming back.