But you and I both know I'm right. If there were two separate Batmans and Supermans and Wonder Womans and Flashes then there would be endless debates amongst the fan base as to who is the better one and how one should replace the other one and so on and so forth. Honestly, I think it's just the way Hollywood is built when actors are cast as these iconic characters. Once they're cast and assuming they play the role well and people gravitate towards them, they ARE the embodiment of their role for however long they have it. Christian Bale WAS Batman and no one else was allowed to be Batman during his time. Christopher Reeve WAS Superman and no one else was allowed to be him while he was Superman. Its how Hollywood wants it and its how the people want it. They want one definitive version at a time. You can't deny, man, that if Chris Pine was cast as Barry Allen/ Flash tomorrow then that would seriously take the wind of out of Grant Gustin's sails, especially since his show hasn't even started yet!
Now, to be fair, one could make the argument in the case of Sherlock Holmes who currently has, like, 3 different interpretations of him in tv and film simultaneously. The difference, I think, between Sherlock and Batman or Superman or the Flash is that Sherlock is a very malleable character and you can have multiple very, VERY different interpretations of the character to the point where its pretty much "Sherlock" in name only. I don't this kind of multiplicity could work with mainstream superheroes in this day and age.
