If you're trying to be original, yes, it's kind of important. If you're just trying to write something entertaining, not especially.
Ultimately, most stories are about the same thing: how characters react to situations. You can merge them with great settings, cool mechanics (Butcher magic rocks!), and whatever good idea you want, but if the characters are dislikeable or just boring, the whole thing becomes that way. Think about all the genres of fantasy out there. Take Terry Pratchett, J. K. Rowling, Jim Butcher, and J. R. R. Tolkien. All of them are widely regarded as great authors. Despite all their nice gimmicks, though, it's the characters which make the stories worth telling. Substitute a bunch of nameless mannequins into LOTR, and nobody cares about it. Take Terry Pratchett's narrative and voices away, and you have some mildly entertaining fairy tales. Stripped down, the stories are the same: protagonist faces problem. Protagonist meets supporting characters. Protagonist and Supporting characters fight evil antagonist.
What you need to make a story riveting varies. With some writers it's their voices. With others it's their humor. With still others it's characters, philosophy, you name it. That isn't to say that elements like setting, mechanics and other aren't important though. I wouldn't be half as interested in the Dresden Files if they weren't the magical mysteries they are. But if that's all they were, they wouldn't be enough either.
So for your story(ies), you need to figure what it is you can do which makes it interesting. Write experimentally, and see what other people think. They're you're target audience after all.