All three have essentially the same wheelbase and the first two have quite similar basic bodies, so just by looking at them, I can't be sure that the 2009 Muranos isn't a major facelift of the original. The 2015 Murano has similar doors, but the top has a stronger curve front and rear, so at a minimum there was major work done. (Murano mavens, please comment regarding these observations.)
The initial Murano featured a somewhat symmetrical front/rear fender profile that displeased me when I first saw it. It gave the vehicle a static appearance. Apparently Nissan stylists, the car-buying public or both came to a similar conclusion because that feature was ever more strongly eliminated in the succeeding models.