it lacks real 'meaning' it is a concept.....and an 'ideal concept' at that......'greatest' 'best' etc. are the extremes of ideals - and a euphimism for the 'best' we've 'seen' so far......
greatest means what it means.... Its just an english word...i am not able to find some great philosophical meaning to it
Greatest is up to each individual to place value on. If you deem something great or the greatest then you give it a high value ranking in your life.
Roger Federer - the greatest tennis pla
Seabiscuit - the greatest racehorse.
Lestat - the greatest vampire.
Johnny Depp - the greatest actor.
The best in the world at what you do.
Mohammed Ali- He was in his own words-the greatest. I believe him.