This is difficult to choose.
Susan Graham and Gregory Kunde seem very much in tune with each other.
But when they're on, no one makes music together better than Angela Gheorghiu and Roberto Alagna.
The classic version is this one with Tatiana Troyanos and Placido Domingo. They sing big. This was my introduction to Berlioz' Les Troyens. This film is a shortened version.
So I offer this one with Verrett and Gedda.
Perhaps you have a favorite.