It is an argument which has raged for decades and divided boxing fans the world over.
And after Vasyl Lomachenko was beaten by Teofimo Lopez last weekend, the debate over who tops boxing's pound-for-pound list has been reignited.
Lomachenko was widely considered to be the best in the world but his defeat raises questions over his standing.
Canelo Alvarez is the most likely candidate as he considers his next move but Tyson Fury may object having regained his crown as the heavyweight world champion.
And now you have your chance to name your top 10 fighters with our survey - just drag your top 10 into position below.
Lower down the weights, welterweight champion Terence Crawford and bantamweight ruler Naoya Inoue would also have a strong case.
Both men will be in action later this year with Crawford taking on Britain's own Kell Brook while Inoue defends his two belts against Jason Moloney on Halloween.
For those who name Canelo as their No.1, the Mexican unsurprisingly agrees.
"I've done better than they have," he said of his rivals.
"I've done things that are better than they have done. It’s never really not allowed me to sleep, to not be No.1 pound-for-pound.
"Because at the end, there’s somebody who puts you there. Maybe those people don't like me, and they’ll never place me at No.1.
"The only point here is I felt No. 1 my entire life; tat’s why I have reached where I've reached.
"Ever since I started my profession, I felt No.1 and I continue feeling the same way. And I continue training as though I were No.1, and I’ll continue doing that my entire life."
