I think the question could have been worded better. There's a difference between "most popular" and "best".
The most popular will have to be the '80s perm (as in '84-to-'87-ish, 'cause the "New Jersey" era had a different touch, and unfortunately the media for some reason seem to love to pick on that particular period of time and make fun of it, which makes it "popular").
Of course, the "Keep The Faith" 'do was perceived as nothing short of revolutionary, so that might be considered pretty popular as well.

As for the best, hard to pick. They were all nice and fit to their time. I'll probably go with 1989-1990 and 1995. Which means, in the poll, I'll vote "The These Days era".