In lyrical and romantic repertory, Gigli was regarded as the legitimate heir of Caruso (Martinelli excelled in the more dramatic and heroic parts).
Smoothness, sweetness and fluency were the outstanding marks of Gigli’s singing. His style was essentially popular, both in its virtues and its limitations: natural, vital and spontaneous on the one hand, but always liable to faults of taste — to a sentimental style of portamento, for instance, or the breaking of the line by sobs, or ostentatious bids for stage applause “like a beggar appealing for alms” (Ernest Newman). He missed refinement in Mozart, and was unequal to the technical demands of “Il mio tesoro”; in Verdi he was more at home, although notably happier when, as in the second scene of Un ballo in maschera or the last act of Rigoletto, his grandees had adopted popular disguise; best of all in Puccini and the melodramatic lyricism of Andrea Chénier and La Gioconda. His mellifluous cantilena in such pieces as Nadir’s romance in Les pêcheurs de perles was consummately beautiful. Gigli was something less than a great artist; but as a singer pure and simple he was among the greatest.
— Desmond Shawe-Taylor