It's difficult to give a meaningful answer to this question, because it's so hard to make a meaningful comparison between popular singers, jazz singers, blues singers, folk singers, rock singers, and opera singers, to say nothing of the difficulty of comparing tenors, baritones, and basses. But given all that, the majority of those who are truly knowledgeable about the human voice and the art of singing, if pressed for an answer to this question, would say that the greatest male singer of the 20th century was Italian tenor Enrico Caruso (born Naples 1873, died Naples 1921), the man whose name became virtually synonymous with great singing. You won't find many who know what they're talking about who would disagree with this judgment. Fortunately for posterity, Caruso made many recordings, all by the acoustic process, and did more than any other single artist to popularize the phonograph (or gramophone) in its early decades.
