He's right on a lot of them. 2 or 3 I disagree a bit with. I was never a fan of Vidic personally (good backs to the wall CB but they go well OTT about him) and could definitely see Gabriel being better than him. I think Rio is right in picking himself over Saliba, but Saliba could overtake him in future.
Brown was a good player, he's right, but over Timber is pretty biased. Park was a buzzy hard worker who could pop up with a goal. Not a big fan of him but Martinelli hasn't pulled up many trees either.
It makes sense that United's forward or midfield players like Ronaldo, Scholes, Carrick, Giggs and Rooney easily win out. Though I like Rice, Zubimendi and Saka too.
To be fair to Rio, he makes clear at the end that the Arsenal guys are currently writing their chapter. He's not saying they cannot beat out some of the United players (I don't think they will), just that they have more work to do.
He seems more normal there than usual Rio, because he usually annoys me.
Edit: I am surprised they didn't mention Neville as the RB rather than Brown. I know Ferguson mixed it up a bit. Could also name Saha or someone like that over Park.