difference between "it" vs "this" vs "that"

Question

Can any native speaker tell me whether I should use it, this, or that in the following context?

John: Have you ever seen the movie "Titanic"?

Me: Yes, It/this/that is a great movie.

To me, 'That' sounds the best and there is no place to use this here at all. What do you think, native speakers?

And I am providing one more context to be clearer. 

John: Hey subha, I've come to know that you went to a theater to watch "La La Land" last night. How is the movie?

Me: It/that is a great movie, probably the best movie I have ever seen.

Answer 1

We use both it and that to refer to things that have just been written or talked about.

I had pizza at Lombardi’s yesterday. It was delicious.

I had pizza at Lombardi’s yesterday. That was delicious.

Grammatically, both it and that are used the same way. However, there is a difference in the meaning or nuance. On one hand, it doesn’t have any particular or special nuance or emphasis. On the other hand, that is more emphatic and carries the nuance that the thing just mentioned is special or interesting.

I had pizza at Lombardi’s yesterday. It was delicious.

It simply takes the place of the noun, pizza, with no additional nuance.

I had pizza at Lombardi’s yesterday. That was delicious.

That also takes the place of the noun, pizza, but adds the nuance that the pizza mentioned was especially and uniquely delicious.

Answer Source It V/s That

Answer 2

John: I see you are holding in your hand a copy of "Titanic"?

Me: Yes, this is a great movie (points to the copy of the movie in his hand).

this requires a very specific reference that is near you.

John: I see (across the street) that the cinema is playing "Titanic"?

Me: Yes, that is a great movie (points at the cinema across the street).

that requires a very specific reference that is away from you.

John: Have you ever seen the movie "Titanic"?

Me: Yes, it is a great movie.

it is a loose reference.