I think that there is a lot of revisionism in the concept of "genius". Just look at the movie "Amadeus". It looks like Mozart genius is the envy of the mediocre Salieri. In fact, Salieri was an incredible composer himself. Then you have people like John Carmack. He is a figure in the game industry. But one of the best Doom ever has been developed without him. The solitary genius creates an interesting narrative, but…
Carmack has never been famous as a game designer. How good or bad his games turned out to be had a lot more to do with Romero, who actually did the game and level design work.
Carmack is worshipped as a game technologist. The legendary stories about him are all based on achieving things with limited hardware. For that he has few modern rivals.