The best genetics for what?
A person could have the best genetics for aesthetics. In this case he'd have to be at least 6' tall.
A person could have the best genetics for building muscle mass. In this case height would not be so important.
My vote: Arnold for one of the most aesthetically pleasing physique.
Just imagine what he would have looked like now in the 2000's with modern drug technology.
For maximum muscle mass with aesthetics: Jay Cutler