Datsyuk and a a disclaimer that Fedorov Wings jersey was the first I ever got and one of my all-time favourites even know I learned more about him as I got older.
Anywho the knock on Fedorov should be that like Brett Hull he has a pretty ridiculous peak stretch but the more you extend the window the worse it gets and THEN you start accounting for the support in terms he played for. I mean, yes he was one of the best players on SOME of those teams but it's really hard to evaluate overall when they become so ostensibly stacked.
If you're asking me on an even level if I take 10 years of Fedorov or 10 years of Datsyuk I'm going Datsyuk. Also how his 98 season turned out has to be considered as it's fairly different from Datsyuk being way older opting to leave to go home. Fedorov essentially had 92-96 as 5 top level seasons and if you count 02-03 as has been mentioned many times a contract year he all of a sudden seemed to put up better numbers. That 92-96 stretch includes a shortened season which ultimately saw a sweep in the Final where on paper he looks like the only guy who tried but of his team leading 5 points and 3 goals, 2 of those goals came in complete garbage time down 0-5 in the 3rd. What I'm saying is before the team went into stacked mode though still with Coffey and Lidstrom, he wasn't exactly this legendary force.
Datsyuk carried his team in a lot of seasons with Zetterberg having nagging injuries and Lidstrom aging. I remember those teams well since I saw them live many times and let me tell you Datsyuk was such an anchor those would have been struggling years without him. And I really don't think we have the 08-09 success without him either despite Zetterberg getting the Smythe in 08.
Again, here's what I focus on with Dats: Much longer period of consistency and reliability, elevating the team.
Fedorov was clearly the more talented player but was more a singular force that at his peak was one of the greatest of all time, as a singular force. Datsyuk was just as reliable defensively but obviously not as much offensively though still top level.
I also think there's something to be said how Datsyuk might get his jersey retired whereas Fedorov never will. And let's not beat around the bush how post Wings, Fedorov didn't have much of a career.