I think this is an interesting question and the only thing certain to me is the answer being uncertain. I think it fair to compare Griner to Abdul-Jabbar in terms of their dominant impact on the game. Yet no one talks about Jabbar as the best ever, though we can forgive ETT his homerism. Either Jordan or now James is most often lifted up in that best ever category, though perhaps Kibitzer might throw Russell into that consideration as well. As for Jordan and James, EDD comes closest to their skill sets, Diggins comes closest to their will and toughness. For that matter, let's toss Magic into the discussion. Jabbar goes down, no problem. Johnson just takes over playing center for him. Johnson goes down and that Lakers team is sunk.
Griner will likely be joining Taurasi, very comparable to Jabbar and Johnson teaming up together. In a sense that will get in the way of the comparisons. I expect Phoenix to be very hard to beat with that combination and obviously it won't be just because Griner carries them. On the other hand, if the EDD or Diggins teams perform at the same level as Phoenix, that likely favors the comparison of either player over Griner. In a sense, by teaming up with Taurasi, Griner is in a no-win situation in terms of ever being considered best player ever. It will not be until those two are apart that Griner will get best ever consideration if she deserves it.