In the world without Francis, Fedorov, Datsyuk, and Bergeron... I'm not sure Barkov is better than Kopitar.
I don't remember enough about Ron Francis but the rest I have watched all their careers.
Barkov is like a Fedorov/Datsyuk hybrid in a larger frame. He has all the puck skills of Datsyuk, defensively he might be better than both because of same level hockey IQ but bigger reach.
Bergeron was amazing defensively, on par with the above and he did a lot of things that just shine in defensive stats.
He's better at faceoffs and that makes up for a lot of the possession difference. A clear advantage to Bergeron. Offensively Barkov is better, his hands and vision, passing are on a higher level in my opinion.
I think Bergeron earned his Selkes and he's probably the best defensive forward. Today Barkov is that though.