Unpopular opinion. Kumar Sanu is a way better singer than Mohammed Rafi.

Rafi was a star only because his contemporaries - Kishore Kumar, Manna Dey and Mukesh were also mediocre. Think of him as Sampras in Bruguera/Agassi/Chang mediocre era

Sanu reigned when Babul Supriyo, Sukhwinder and Udit were also acting. Federer in Nadal/Djokovic era

If Rafi was singing now, he would at best be a Kunal Ganjawala or Kailash Kher level.

Not Sonu Nigam/Sanu level virtuoso

Rafi was Sachin in a mediocre lineup.

Sanu is a much better Rohit in a competitive lineup.

RD Burman and Rajesh Roshan plagiarised simple tunes for Rafi, Kishore etc to sing.

Anu Malik, Pritam etc plagiarize much more complicated Korean and East European songs. Needs the superior talent of a Sanu or Sonu to sing successfully

Rafi wouldnt even be able to pull off a Viju Shah melody let alone a Pritam one