Bob Marley’s music will never die, because, it speaks to the majority of the human experience; oppression, under-privilege, subjugation, disenfranchisement, relegation, predatory practices, etc. And, it’s encoded in English; the dominant language of global mass-media.
Another reason he is the greatest is that no artist can come close to the raw emotions Marley portrayed because as he was rising in stardom, he was still in the middle of a major political war in his country and even had an assassination attempt on his life. So all of those REAL emotions went into the music making it that much more powerful. Marley always kept the music PURE though, and I applaud that.
There have been many amazing artists over time, I believe all the truly good artists have come and past, but Marley sits at the top in my book. His music will literally play on forever and his name will never be forgotten, because LEGENDS never die!