Nikdom, as to Borg and Nadal, there's also indoors, Wimbledon and hard courts, plus influence on the Game in many respects. So, it's not just clay dominance. Borg and Nadal are basically both way up there in the history of clay courters, of course. In addition, beauty is in the eye of the beholder. Plus, I don't find Nadal's game to be ugly either.
I generally find many styles of tennis to be quite pleasing to the eye, whether it's S&V, all court, or primarily baseline play.
This is some beautiful tennis play.
(Borg vs. Lendl indoors in Jan. 1981 at the Masters YEC)
(Borg vs. Connors on rubico in '79, Pepsi Grand Slam, 4 man invitational, only for players that had won a major, big money event played in FLA back then)
(Borg vs. Pecci, 1979 FO final)
(Borg vs. Nastase, 1976 W final)
Thanks for the videos Borgforever and Krosero.