While Red Bull has demolished the competition in 2023, its RB19 winning all 12 races so far, Horner thinks Verstappen's dominance over Perez and the ease with which he executed his eighth consecutive race win shows F1 is witnessing "once in a generation" displays.
"I think there was superiority over everybody at the moment. Generally, it has been outstanding," Horner said.
"And what we're witnessing with Max at the moment is something that you see once in a generation.
Asked what Verstappen, who is marching to his third consecutive drivers' world championship, can do with the Red Bull that Perez can't, Horner replied: "Like all the great drivers, he just has that extra capacity.
"What we're witnessing and seeing with him at the moment is his ability to read the tyre, to read a race, to extract absolutely everything out of it.
"It's great to see. I think he's just at the top of his form at the moment."
When Autosport quizzed Red Bull's advisor Helmut Marko as to whether Verstappen still manages to surprise him with his form, the Austrian replied: "Well, if you are eight-tenths ahead in qualifying, then you know there is still some reserve and some extra margin.
"But it is also about how smart and clever his driving is nowadays. He thinks about all the overtaking moves and can read the races incredibly well. That is what you hear in these conversations with his race engineer as well.
"It is unbelievable what he is showing at the moment, but that goes for the whole team. There is almost no pitstop slower than 2.5 seconds, the strategy is fine, and we haven’t had technical issues so far, so the entire team is doing an unbelievable job."
Verstappen heads into F1's summer break on 314 points compared to 189 for Perez, with the Dutchman mathematically able to seal his third world title as early as September's Japanese Grand Prix, as he did in 2022.
Additional reporting by Ronald Vording
