This is so hilarious to me. I don't think there is an instance of him saying he's a genius. Regardless, you're inferring a person whose ran/started several multi billion dollar companies, in a variety of fields, as well as teaching himself to design literal rockets, is just like a slightly above average guy.

There are many, many people with close relations to him who would call him a genius, but yes, I'm sure you know the 'truth'.

'I think Elon Musk is a genius and I don't use that word lightly. I think he's also one of the boldest men that ever came down the pike. Put me down as saying I've always been afraid of the guy whose IQ is 190 and he thinks it's 250. I like to think there’s a little of that risk with Elon. He is a certified genius.' - Charlie Munger.