But that's it, he only beat two names. Beat them well but you could say that Hopkins was still a neophyte when he fought Roy.
You want two names:
Floyd for a start, beat JMM, made it look easy, beat Canelo, made it look easy. Beat Pacman, made it look easy. Also beat Cotto, made it look easy. Beat DLH, made it look easy. That's five names alone. That's without mentioning Conor.
SRL. Beat Benitez. Beat Duran, second time, made it look easy. Beat him again. Beat Hearns. Beat Hagler. You just can't compare RJJ's resume.
And you asked if there is a threshold for someone to be considered an ATG, I would say more than two if we are going on accomplishments. Especially when compared to guys like PBF and SRL who have almost half a dozen big names on their record. Don't get me wrong on Prime RJJ I think he is the best P4P EVER BUT not on acheivements, on perceived ability. There is a difference.