I have recently spoken with others about the objective of being the greatest of all time. It seems to me that this is often interpreted as arrogance, or unrealistic, or immeasurable, or selfish. In my opinion, it is none of these things. That is because becoming the goat is not about overshadowing the achievements of one's predecessors, just as it is not about detracting from the potential of the future. It is rather the act of, at a specific point of time, pushing the limit of human progress to a new high.
Bringing humanity to a new level is an excellent goal even though one must resign themselves to the reality that it is likely that there will never be a moment in their lives when they can say that "right now, I am the greatest of all time." Even if at some point they hit the target, it will have been them ten minutes ago, or them ten days ago, or even ten years ago. And so one needs to work harder to attain that moment once again.
Besides that, the notion that one should hold on to the title is not only ridiculous but it also corrupts the purpose of the task. Newton, Galileo, Hooke, were all at the forefront of their fields in their times, and yet now most high school students know more about their sciences than they did. That does not take away from their achievements, in fact it is a positive outcome of their greatness. The same is true in sports. By his own admission, Garry Kasparov would never have bested the chess player that Magnus Carlsen has become now. This does not make him any less of a legend, it is merely a consequence of the fact that we know far more about the game now than we did then, in large part because of Kasparov himself. This is a healthy approach to being on top of the world.
To me, being the greatest of all time is motivation to push your work to new highs. It is not arrogance or selfishness unless you actively seek to hold the title forever. Just as it is neither immeasurable nor unrealistic because you need only measure yourself by how far your predecessors got as opposed to the infinite potential of the future.