Cleopatra is the selling point but the resurrection of a long-lost world is the strength of a powerful new exhibition at the Franklin Institute in Philadelphia. Edward Rothstein reviews “Cleopatra: The Search for the Last Queen of Egypt” and finds, “the wonder we feel is not at Cleopatra’s beauty (which Plutarch reports was “in itself not altogether incomparable”) but at the extraordinary cultural universe that preceded her and surrounded her before Egypt submitted to the Romans in 30 B.C. and Cleopatra — Egypt’s last pharaoh and the end of the Ptolemaic dynasty — committed suicide.”