Mm... I could maybe see Zetterberg over Datsyuk, but I think that's splitting hairs.
I don't think they should be above Delvecchio or Fedorov, though. For Delvecchio, he was basically a point-per-game player from 1954 to 1970, and was good before and after those years, too. He won three Cups (was a big part of two of them), as well. Maybe the peak couple of seasons of Datsyuk or Zetterberg are above his, but when you factor in the longevity, the winning, and the consistency, I think Delvecchio edges them both, but I concede it is close.
For Fedorov -- and it's a bit like when someone thought I ranked Draisaitl too high for Edmonton -- I take into account a Hart trophy / Art Ross season. That is really big, for me. If you reached that level, you are at the level of "best player in the world", at least briefly. Now, Fedorov didn't win the scoring race in 1993-94, but he was close, and 1st-team All Star, Hart trophy, Pearson, and Selke in the same season is crazy. Sometimes there is just a point where the peak is so high, it gives the player extra weighting (by contrast, the peaks of Zetterberg or Datsuyk aren't as high).