The same thing that Shanny lacks. And Datsyuk. And Z. It's not something that only comes with numbers, and I've already admitted this is a messy thing that I find hard defining, and that it's something that is likely highly personal.
Fedorov doesn't define the Wings for me. When I picture those teams from the 90s, he's not the face of it. He was an essential piece to it's success, though I think Shanny was, too. But Yzerman is the guy I see as the wings. Lidstrom is the guy I see after that, though I think to a degree less than Yzerman. Honestly, I wouldn't have been disturbed by Lids' number not being retired.
To get your number retired, by the Wings, you have to be a great player. Obviously. But I think you need that something that makes you unquestionably a great Wing. For me, Fedorov doesn't have that intangible thing. But, as I said earlier, I also wouldn't complain if they did retire his number. I would push for Z to be next, though.