+3
Unless you've read all these scripts, one can't really say. And I don't mean a transcript of the movie, but the script in its final draft or at least shooting version. Until then you don't know how much was added or subtracted by the director and actors on the set, or by the director and editor in the editing room. You're judging by the final product on the screen, which may be attributed to the screenplay and its writing in varying degrees.
Casablanca is rather famous for being written very much as they were shooting, that there wasn't a "finished" script with full structure and dialogue even as the cameras were rolling, instead being changed as they went. The Godfathers and Rashômon are adaptation of existing material, and Strangelove a loose adaptation. Pulp Fiction has uncredited nods to many sources. Kane, Rashômon, Pulp Fiction, Strangelove and The Godfathers have their directors as credited co-writers. Hannah and Her Sisters is the only one that has a singular writer who was also the director and heavily involved in the editing process, so that film would have to be the most "pure" from page to screen, and any alterations along the way were by the same voice and mind that created the script, discounting what each actor added and the set dresser and the cinematographer and on an on..
So you're judging by, what? Consistency of voice? Complexity of narrative? Or just the movie you like the best and, therefore, it must have the "best" screenplay?
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"Film is a disease. When it infects your bloodstream it takes over as the number one hormone. It bosses the enzymes, directs the pineal gland, plays Iago to your psyche. As with heroin, the antidote to Film is more Film." - Frank Capra