He is insanely good. And I still think Willy is his equal. The difference there is that Marner plays on the league's best PP unit, and Willy is on a PP unit that is among the league's worst*. I wouldn't be surprised if that changed to next season and added some 10 points to Nylander, maybe more.
* Not taking away credit here. Marner is the QB on that unit, and the single biggest reason that it is so good. The second unit is more interesting. It's all about Willy and Auston. The puck carrier attacks the net, forcing the defense to respect their shot. Either they take it, or use the lanes for a golden road pass to the other. Everybody else on that unit is a prop. What has happened is that they struggled, and then got their spots switched for a month or so. That change made things a whole lot worse, and now they are out of sync. That's a problem because their main weapon is also pretty much their only weapon. Brown and Marleau have been abysmal, which just makes the puck carrier all the more isolated.