I would never argue that there was a straight up, black and white "unit of measure"... There's not. But there are hazy outlines.
Example. Just getting an Oscar does not, in and of itself, mean you are "the best" or "better" than any other actor. However, if you have won *several* Oscars, and are generally praised across the board for your consistently well crafted and executed performances, then several unquantifiable hazy outlines suddenly begin to form a clearer overall picture....and it is at that point that you can probably point to that particular actor as being "better" than the schlup on your block who is constantly getting turned down for every acting job he tries out for, because he simply has not succeeded in convincing a single person (out of possibly hundreds of people that judge it for a living) that he can act in any way, shape or form.