If the goal is to be the best in the world for the sake of being the best in the world at something, just pick something really obscure.
I'm the best in the world a tactical boomerang juggling in Breath of the Wild. A gamer with pro-level skills could probably show me up with a few hours practice, but until someone decides to do that, I'm the best.
I think the goal is to be best in the world at something that society will reward, that will enable you provide it with something it wants that it doesn't know how to get or doesn't know it wants yet.
In your case, making entertaining videos of popular games is a pretty profitable niche.
I'm the best in the world a tactical boomerang juggling in Breath of the Wild. A gamer with pro-level skills could probably show me up with a few hours practice, but until someone decides to do that, I'm the best.