What has Satan ever done, anyway? Come on. In the 1980's, all he did was infest metal records and tell teenagers to kill themselves. In the 50's, he infested Elvis's hips. He never did any real damage, he was just kind of a background influence out to annoy.
Cthulhu, on the other hand, is the real terror here, perhaps precisely because we have no idea what he is truly capable of, not having awoken from his slumber. Whatever it is he can do, surely it's better than Satan. All he's doing is messing with record needles and speaking backwards into the microphone whenever Judas Priest records their guitars.