A two-handed backhand is a functional, stable and safe tennis shot with many advantages. Elegance is not one of them
With that out of the way, I would vote for Nalbandian among current players and Miroslav Mecir and Chris Evert among past players.
Djokovic, not so much. And the less said about Nadal, the better. If any aspect of Nadal's game appears elegant to you, then I could also convince you that I am George Clooney.