This sentence is from Michael Swan's "Practical English Usage". It's about the difference between "it" and "this".
"I enjoyed Vampires' Picnic. It/this is a film for all the family."
"VAMPIRES PICNIC: This is a film for all the family." Using "it" is wrong in the second sentence, because "this" is preferred when we bring things into focus" according to the book. But is using "that" wrong in both sentences?
We tend to use "this" to refer to something close at hand, and "that" for something not immediately in front of us. For example, if you were at a party and your friend pointed out someone across the room, they might say "that is my sister"; whereas if they were introducing you to the same person they would likely say "this is my sister".
When it comes to things less tangible like your example of a film, the choice of 'this' or 'that' could depend on a number of factors. If someone mentioned a film that they had seen a long time ago, you might say "that is a great film!", because it isn't immediately at hand. If you were watching a film along with your friend, you might comment during the film "this is great!", because the film is currently right in front of you.
In the context of your example, it sounds like someone is reviewing a film that they have just seen. Because the film is the subject matter currently being discussed, using "this" is appropriate. Subjects under discussion are sometimes metaphorically referred to as being "on the table", so it is as if the subject matter is in front of you. Your first example would make grammatical sense with "that", but it makes the film sound less current. The second example doesn't really work with 'that' because of the way it introduces the film title - it brings the subject to you first, so it seems wrong to then use the more remote 'that' to refer to it.
