Movie Thoughts - Is This the Right Time?

I've been struggling for the past year or so with trying to introduce some of the classic children films to my daughter (who is four and a half now). I tried A Christmas Story about six months back, but she lasted about half an hour before leaving. I am aware that her attention span is around the 30-45 minute mark in a theater (while watching any children's animation/film) and that is reduced even more at home because obviously there are a lot more distractions at home. In fact, a while back I tried to have a movie play date at home for some of her school friends, but they all lasted about 30 minutes into Toy Story before they were off playing with the kitchen set.
While my daughter is addicted to Peppa Pig, Dora and Chotta Bheem (Indian Cartoon), I have desperately been waiting her to watch movies like Chitty Chitty Bang Bang, or Goonies, or even Mary Poppins, but alas I have been unsuccessful. The only full length animated feature she has managed to sit through, and does so repeatedly, is Tangled. So there seems to be some hope after all.
The reason why I bring up this discussion now is because this morning my daughter woke up and told me about a dream she had. According to her, she dreamt about being in space going to different planets where aliens live. So, the little light bulb on top of my head suddenly lightened up. Could this be the right time to maybe show her E.T.? She is all into aliens right about now and fascinated by their existence (or lack of), so could this be the moment I have been waiting for? As it happens I have wanted to buy some DVDs of movies that I watched as a kid and this might just be the moment I take that step and try showing them to my daughter.  
The truth remains that I can't wait for her to someday be as crazy about films as I am, but what the future holds I do not know. What do you think is the best time to introduce classic films to kids? Should I go ahead and show her E.T. and see what she thinks, or maybe wait a while? I mean the other day during #MTOS (Movie Talk On Sunday on Twitter) someone mentioned watching Rocky Horror Picture Show at 4, so E.T. should be okay?