It does if that’s the explicit question being asked. If all things were equal, budget, quality of direction, acting, special effects, etc. how much would the script bring to the table in terms of entertaining the audience?
Both screenplays and stage plays are perfectly readable things. If they’re not good to read, they’re probably not going to be good when performed either. The only qualifier to that would seem to be if you can snazz it up enough with special effects that outdo everything else to-date, that the audience forgets about what’s actually happening.
None of these three films would be a great read. Star Wars would probably be the best, but still pretty sub-par. All of them only have any chance in hell of succeeding on the screen by virtue of pulling the wool over the audience’s eyes. But, that’s not what the script brings to the table. That’s what the director and the money man bring to the table.
What the script brings to the table is what you get if you read through the script. Nothing more and nothing less. And what it has to bring is an enjoyable time for the reader.
But again, the key criteria of a script and of a movie is that it is entertaining. A script which is entertaining merely based on the strength of its dialogue is better than a script which carefully constructs a five act story structure, utilizes deus ex machina as an explicit homage to ancient Greek plays, and is boring as crap.
Having a story broken into acts, having each scene modulate the tone from uplifting-to-downbeat-and-back, creating a strong A plot and good B plots, using proven character archetypes, etc. aren’t aspects of a good script. People learn those in storywriting classes because they are useful tools for creating something entertaining. Following the rules allows you to construct something even when you’re out of ideas. You can take all the rules, roll a dice to decide from among the legal options, and come up with something that will be entertaining because it conforms to the list of options for known entertaining story structure. Writers learn story structure because a working writer needs to be able to generate content, regardless of how creative he is feeling, if he wants to eat.
Conformance to standardized story structure isn’t good scripting. An amazing script is one which conforms to no known rules and yet is still highly entertaining. That would be a script which is a masterful work and which should be applauded by anyone who feels like ranking this sort of thing.
That’s irrelevant to the movies under discussion, none of which is particularly marvelous. But the point remains that your argument doesn’t apply to any method of ranking of scripts outside, perhaps, of a classroom that is teaching story structure. Outside the classroom, scripts are ranked by entertainment, inventiveness, and artistic merit. For the movies we are discussing, the latter two are both a nill. For entertainment, the Avengers and Star Wars would probably be amusing but unimpressive reads. Avatar would be another nill.