I caught the tail end of Delvecchio's career...Looking st his numbers..he was a very steady performer. Had two very good seasons after turning 40...like Federov...he was never really "the man" on his teams, that distinction belonged to Gordie....and in the case of Federov, Yzerman.
I don't know that Pavel was ever the man either. He was always linked to Z and of course Lidstrom...
In terms of pure talent, Federov was probably more gifted than both of them, but Federov may be the most physically gifted player I've seen here going back 50+ years.
Delvecchio and Pavel were more traditional C's who facilitated more than they scored. Federov was more of a goal scorer. They all played into their late 30's / early 40's.
Super close but I'd probably go Delvecchio..then Federov then Datsyuk.