It doesn't matter if it is appealing or not, actually no fictional character is appealing per se, it's the stories told about them that make them appealing or not. Superman is not appealing now because they are making ****** Superman movies. Make a good movie, like it has been done before and the character is a sensation. Batman is appealing 'cause (mostly) good stories were told in the Nolan era. Make a Batman & Robin and the appealing is gone, no matter the character.
WHAT MATTERS is how well known is the character: If the character is known to the audiences, then it's just a matter of making a good film, and you will capture a good portion of the attention of the public in no time, regardless of marketing. And Superman and Batman have all that in spades. Make a WILDCats movie, it's a marketing uphill battle. Make a BvS movie, you have everything on the table to feast.