I agree totally with what @Napoleon Wilson has said about the site's policy. However, I just want to clarify something. You say: Should I create a tag for every movie which has no tag yet?
Obviously, no. Don't go on a mass creation spree where you create a new tag for every single movie in history, regardless of its activity on this site.
Your next comment was: I don't want to create a tag for every movie on the planet ;-) Only movies I want to ask a question about at the moment.
Yes. That's the way to go about it. If you have a question and a tag doesn't exist, create one. Otherwise don't.
That might be incredibly obvious, but given the wording of your question I just wanted to absolutely clarify it.