Very possible. If players were judged solely on the best 3-4 years of their careers, I would agree that he would be the best ever.Random thought that I've been thinking about. JJ Watt has not had the career of Bruce Smith or Reggie White overall but I feel like when he was in his prime he was even better than both of those guys and this is coming from someone who watched both of those guys very closely growing up they were my 2 favorites. I was always obsessed with the DE position, loved playing that position and loved watching it. I feel like peak Watt was better than Smith and White because Watt never had the surrounding cast around him that Bruce and Reggie had.
Teams didn't have the luxury of concentrating on Bruce Smith or Reggie White the way teams did/do JJ because look at who else they had to deal with on those defenses. Reggie in his prime with the Eagles had Clyde Simmons, Seth Joyner, and Jerome Brown around him with Eric Allen in the secondary. Then in Green Bay later he was surrounded by Sean Jones, Gilbert Brown, Santana Dotson with a secondary that had Leroy Butler and Eugene Robinson. And with Bruce Smith on the Bills youre talking Leon Seals, Cornelius Bennett, Daryl Talley.
Had JJ had talent around him on defense like that who knows what he could have done or how much longer his prime might have been. As much as I love Reader and Mercilus and Mckinney those guys are just nowhere near the level of some of the talent that White and Smith had around them on those units all those years. Even without the supporting cast like what Smith and White had JJ was doing things in his peak that those guys weren't doing. So yes, seeing what I seen and knowing what I know I do feel like JJ in his prime was the best defensive end to ever play the game.