The problem with this kind of question is it's opinion based and therefore, subjective. No doubt this has been linked many times before but I'll do it again: see Good Subjective, Bad Subjective.
StackExchange, in general, shuns subjective questions, and rightly so. Without objective answer-judging criteria, the award of the surprisingly highly-prized check mark is completely down to the OP and there are no grounds on which other people can object to this.
Now, while the check mark has always been somewhat subjective (it is, after all, for the answer which helped the poster the most), voting should not be subjective. There should be criteria by which people can judge which answer is the best and therefore it will gain votes to float to the top. Without these criteria, all answers are of equal merit and equally deserving of upvotes.
However, the idea that subjective posts don't fit on StackExchange was established fairly early, when most of the sites were about programming, science, hard subjects like that, where a question almost always has a definitive answer. Here we're on a site where creativity and personal opinion are encouraged in answers because it leads to great, creative answers - why not in questions too?
The primarily opinion-based close reason says this:
Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.
Given the nature of worldbuilding, why should we have to provide specific expertise for an answer to be valid? Sure, if it's a scientific question or even hard-science, we expect the answer to be verifiable. But some of our best questions are pure fantasy, which, given that fantasies are all fairly unique, is nigh on impossible to provide facts, references and specific expertise for.
Personally I'd love to see a way for this kind of question to become acceptable here. Come on, we're not exactly a serious topic site: dragons and oversized spiders, anyone? A lot of what we do here is imaginative, creative, fun - and personally, I think that's one of the big reasons this site got going so well. I'd like to see this attitude extend to the content we have.
But. There are always conditions. If we start allowing questions like this, there's going to be friction. How do we differentiate the good subjective questions, like the one in question here, and the bad subjective?
The truth is, as the blog post I linked says, that expertise lies in between objectivity and subjectivity. On many posts, we see differences of opinion, and that's a good thing. It means our community is healthy - we're discussing our points of view on a post, and in general, I find posts are in the state they should be. Bad posts are closed and left that way. Posts that need improving are put on hold, edited, and reopened. Good posts gather lots of upvotes, answers and discussion.
My point here is this: we have a good community. Let's use it. All the subjective posts we get are still subject to community voting and closing: if we get a good subjective, it's likely to stay open; a bad subjective is likely to be closed, just as it is if the post is completely objective. All I would advise here is that we don't vote to close purely because a post is opinion-based or subjective, only if the post has issues.
My opinion in short: we should accept posts like this without voting to close purely due to their subjectivity.