I'm a science fiction author at heart, and what I like about the Cthulhu Mythos setting is that, at its core, it is horror science fiction. I can take ideas from modern theoretical science, manipulate them in truly bizarre and weird ways, and remain true to the Cthulhu Mythos vision.
'Star Wars,' 'Doctor Who,' 'Forgotten Realms,' even 'Firefly' and 'The X-Files' have shared world novels and other media. I can't help but notice these settings have large shelf space in bookstores, so their publishers and authors are getting something right.