The ones from the Early 70's were alright, but when somebody says, 70's Mustang, I still think of the Mustang II. Which was smaller, back down to its original size and weight, but ridiculously neutered, and ridiculously fugly. I can begrudgingly give a hesitant nod to the Cobra II (properly equipped, of course) or the King Cobra. The Fox Body started out basically as a Fairmont coupe, but It came into it's own in the 80's.
I did always think it was kind of stupid that the car stayed on the same Fairmont chassis from 1979 all the way up to 2004, but they did pretty well with it.
As far as the 90's Mustang is concerned, I never really was a fan of it. I've kinda come around in more recent years, but I still don't really care for the jelly-bean styling all Fords had back then; I think they look bloated. Still the styling on the Mustang was nowhere near as bad as that on the Taurus or Escort*; they just seem to have gotten uglier over the years. When they redesigned the Mustang in '99 to look "New Edge", I thought they looked better, but it still took me a few years to warm up to them. The 2003 Cobra, "Terminator" helped a lot though:
as did the Mach 1:
have to admit, I still kinda want one.