I agree, I’m more likely to pick up something with a nice picture, but I’ve spent enough time over the years rummaging through books at fates and markets not to pass up the crappy ones. Example time: One of my fav series growing up was the Authurian Saga. I noticed that they’ve been given a (much needed) facelift when I searched for it just now. This is what that cover of what I think is the worst one in the series that I read looked like, and below it is the reworked version. (Not brilliant, but a whole lot better IMO). I mean which one are you more likely to pick up first?
I mean seriously, yes there is a cave in the story, but in the picture it’s dull and boring (In the story it’s full of crystals). Which publisher actually ok’ed it? I can’t imagine how many people didn’t read it because of the cover.
Anyway, I like relevant and eye catching as well. I think less busy also tends to work better for most (although there are exceptions of busy pictures that look really good) particularly due to the small size of the images. What is “good” though depends on the story, some are great with bright or bold colours, some can be good just by being different to all the others so it makes me stop and wonder what it’s about. Like the cover of demon mask was cool largely because the style of artwork was so creepy and different. I love the bold simplicity of Sea Eternal. Iron destines looks really bold and eye catching enough that I wanted to see what it was about. Anyways I don’t think it’s a one size fits all thing for games, and depends on the story and artist style for what it needs artwork wise.