Conor has been (and remains) the biggest name in the game for about 5 years now. I would say no one else has come close to his level. The second best was probably Ronda at her peak casual popularity tbh and then Brock. How long do you think it will be before someone as popular as Conor comes along? Someone who can sell 1 million+ ppvs even when they fight a washed bum like Cowboy.