Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn."In his house in R'lyeh, dead Cthulhu waits dreaming." -And with that line, a legend was born. H. P. Lovecraft was a genius when it came to thinking of great things lying in wait. Cthulhu is probably one of the best known eldritch horrors known now. He is some kind of god, something to be worshiped by the people of Earth. I know I'm not all correct here. I am not in fact an expert on Lovecraftian gods, but it has always seemed to me that Lovecraft himself didn't like to categorize things such as this, relying instead upon the fear generated by these indescribable entities rather than some simple categorization to keep them straight. Lovecraft was a lot of things, and, it seems to me like he was all about the horror and much less about the whole, let's put these things in nice little packages and put definite names and personalities on them. No, Lovecraft was perfectly happy to inspire dread rather than pure academic interest, and that is the success of his writing.
Cthulhu is incredibly well known today, being both used as a cultural meme and as a sign of some unknown and elder thing that resides, fearfully, in a place that we as humans cannot find him. He is a mysterious figure, and one that cannot be explained. He was thought of by a man, given life by a story, and he resides in culture as something that could almost be the truth. He is not worshiped as far as I know (mostly because he is quite fictional) but there are entire websites and societies dedicated to him. There are countless homages giving praise to this god of fiction. Songs have been written about him, authors have used his likeness in works by themselves. Stephen King pays homage to Cthulhu in his seventh Dark Tower novel as Roland and Susannah rush through the bottom of a broken castle pursued by something that had come through Todash space (the space between worlds). Neil Gaiman has used the character in his story "I, Cthulhu". Even the video game Call of Cthulhu: Dark Corner of the Earth is a reference to this incredible entity.
He has survived for nearly a century as something old and fantastic. And the whole idea of Cthulhu speaks strongly of our cultural identity of wanting something more from life and something interesting. We have religions and holy books and Gods (monotheistic and polytheistic varieties), but none seem to have the fictional hold that Cthulhu does. He doesn't even appear in that many of Lovecraft's works, but that doesn't matter. It's the interest that holds us captive. We want to believe in something that isn't quite an evil God, but rather something that only cares about worship, only cares about consuming, only cares about its own power. It is a twisted version of our own God(s), the Creator(s) of existence, the Force that surrounds us. Cthulhu is a negative force, one bent in destruction and based in darkness. And there is something primal and wrong about that, but also something that feels like it is incredibly right. It makes sense. And we want it to exist because it lends some mystery to the world, something that is rarely present anymore.
Maybe I'm reading too much into the whole thing. Maybe it's simply that Cthulhu has a nice name and was in some good stories, but I have to believe that it's more than that. It hits something in us and makes us nervous in turn, allowing us to wonder if something with that face of an octopus, something wholly, or nearly wholly, alien, could have created us, could have brought us to worship it, and could make us destroy ourselves. It's a fascinating thing to think about, and one that requires a good amount of thought to bring the right theories across.