There is no greatest [blank] of all time. Shawshank and Godfather are great in what they do, but there are films better in some way or another.
Freddie Mercury, while certainly a legend and a superb singer, likely had some singers better than him. Hell, he didn’t consider himself the GOAT, rather Montserrat Caballe, whom not many people know of.
The Beatles were pioneers and amazing, but not the best band. Other successors did what the Beatles did better.
Every media can be good, great, or superb, but there is no best.