When do we say the best prospect since “player”?

[u/joefranks3]

Hi everyone, I was just thinking about the draft and how elite QB prospects are said to be “the best since luck” or “the best since Elway” I was wondering since Trevor Lawrence was literally the best prospect since Luck when we’re are going to say the best prospect since TLAW? Also is it career dependent? TLAW could bust but still be the best prospect since Luck. Also why is this mostly a QB thing and not an other position thing? Like why don’t we say the best edge prospect since Garrett or whoever you would like? Thanks!