Not in the slightest. If he keeps this up for another decade at least, he'll be in consideration for it, but he still has never taken anything less than the strongest squad in a given league and made more of it than the sum of its parts. Since there are other managers who have, and who have also won more overall than he has, it is self-evidently not possible for him to be considered the best manager ever.
Has he won more than anybody else? No.
Has he taken a less-than-top team and elevated it to the top? No.
Has he got a spotless record of legitimacy? Most certainly not.
How is it even possible to posit the argument that he could be the best ever? It's patently absurd. He has done very well, no denying that, but there isn't even one single aspect of his career so far that has not been surpassed by other managers; and until he has shown that he's also able to succeed with something short of the strongest squad that's already favored to win regardless, it's frankly worthy of ridicule to talk of him as the best there ever was.
We're talking about a man who took over Barcelona when they had the strongest team in the history of the sport and did as you would expect of such a thing. He then went to Germany to manage Bayern where winning is essentially guaranteed, but did not succeed in Europe. Then he went to England where he took over a team of cheats who flung money in all directions until nobody else could really compete, and he still has not succeeded in Europe there, either. Even if he does win the CL tomorrow, having not done so since his departure from prime Messi/Xavi/Iniesta eleven years ago, despite having all the means to do so every single year since then, says all that needs to be said about his credentials as a manager. He is by no means bad at his job, but he has never proven that he's more than a man who's good at keeping superstars in line.
How can anyone compare that to someone like SAF who not only proved that he could make miracles happen at Aberdeen, but also elevated United from a position comparable to current-day Tottenham, to two decades of utter dominance, all based not on unlimited funds funneled into the club through dishonest means but by his own sheer credentials as a manager? It isn't possible for a sane person to say that Pep has accomplished more than that. That'd be a declaration of idiocy. Pep will have to continue as he has done for another ten years at least before such a comparison is anything short of laughable, and even then, he has never proven that he can succeed with less than circumstances that already set him up for easy success.
I frankly think that any remotely competent manager would have accomplished all that he has in the route that his career has taken. I'm prepared to say that Klopp has impressed me more, considering the circumstances of what he has had to work with. Nobody can possibly claim that Pep is a bad manager, but I've seen nothing that suggests he has gone above and beyond, and his history of frequent tactical disasters in the CL (which are down to him, personally) says as much about him, if not more, as his domestic titles with teams that were already favored to win regardless of who the manager might have been. It's not as if his transfer record is impressive, either--he has just had so much money at his disposal that his many failures there are irrelevant.
And all of that can be said without even beginning the discussion about the shadow of cheating that has followed his entire career.
