The term aesthetic is one of a favourable visual presentation. Therefore I would suggest there isn't "the most aesthetic of all time" because measures of aesthetics are unique. For example, we don't look for the greatest artwork of all time yet have favorites and value inherent quality.
Melvin Anthony, Frank Zane, Serge Nubret, Arnold Schwarzenegger, Francis Benfatto and Bob Paris are all physiques that come to mind when discussing aesthetics.