I think a lot of factors enter into the acceptances and rejections. This is about a book, not a screenplay. A CORPSE IN THE SOUP, released in September 2006, was picked up unagented but you might enjoy this story anyway.
My sister and I did the usual round of querying agents and received an amazing amount of requests for the first three chapters, etc. We've been told we write a great query letter. Unfortunately our manuscript wasn't holding up as well when we sent in the first three chapters or fifty pages as requested. They didn't want to see the whole thing.
One agent was very kind, said she really liked our characters and story so she gave us lots of advice on what needed to be fixed and suggested that we should find a manuscript consultant for this first book in the series. She clearly stated that she thought it was a good candidate for publication. We took her advice, found a great consultant, did a rewrite and when we sent her a thank you note for her advice months later after our manuscript was polished, we also enclosed the first fifty pages and asked for another shot with her.
We didn't hear anything and figured you only get one go-around. The book got picked up, was released in September 2006 and was getting some really good reviews. Lo and behold, in January 2007---one and a half years after the query if you can believe that, we received back the fifty pages and a handwritten note essentially saying, "The story is too silly for me, I don't like the characters and good luck with someone else." Hmmmm. Were the original advice we received from the person who really liked the characters and story and the rejection letter a year and a half later written by the same person? Gotta wonder. There wasn't a major change in the story or characters.