>I knew that there had been at least some small changes
Here's a comment from Ian McKellen himself, interesting that he links the two films:
"Another point on this, the question that dominates my email: the adaptation of masterpieces from one medium to another is as old as literature. Most of Shakespeare's plays are re-workings of stories, poems or written history. When I moved Richard III from stage to screen, I was determined to make a good film in honour of a great play. Had I left every scene and line of the text intact in the movie, it would not have been a good one. Kurosawa's Throne of Blood, my favourite version of the Macbeth saga, distorts Shakespeare to spectacular effect. The play which inspired it remains intact."
I loved J K Rowlings response to a questioner who asked if she was worried abotut he film adaptation of her book. She said that a bad film adaptation had never reduced the pleasure of reading the original book for her and a good film adaptation had always added to the pleasure.
The difference with something that starts out life as a play is that the play has to live in performance, so no version can ever be "the last word" on the subject, only ever an interpretation.