I mean, Yog-Sothoth may have a mean appetite and he may have a plan to save social security (by eating all elderly people) but none of the other elder gods can really hold a candle to Cthulhu.
Yog-Sothoth hasn't proven to be truly alien enough to be a good dark god. And what about these visions by the overdrugged oracles claiming Yog-Sothoth actually spoke to them?!? I mean come-on, if an elder god "speaks" to you, your brain is fried. Cthulhu wouldn't stand for any of that, he'd send some horrible and unspeakable horror to paint their rooms in the blood of innocents. Before dragging them to eternal torture in some dark hell.
So, when Yog-Sothoth is found to be philandering or doesn't really save Social Security, or if it turns out that he hasn't even read the Necronomicon, or he fails to be evil and alien enough, don't blame me, I voted for Cthulhu.