There's always a certain degree of interactivity between the viewer or consumer of art and entertainment and the work. I'm not going to try to define art, nor will I try to make a sharp distinction between art and entertainment. Instead, I will suggest that such distinctions are best made by the viewer of the work.
Whether we're talking about a novel, a movie, a comic book, a song, or even a painting or sculpture, in all cases, the creator's work is meaningless until the viewer or consumer of the work brings their own ideas and imagination to bear upon the work. Of course, the work has meaning to the creator, but the creator is also a view/consumer of his own work, so the creator actually has a dual role, both in creating the work, and in attributing his own meaning or interpretation to the work. And this meaning or interpretation may be quite different from how others view his work.
Art is largely subjective, because the viewer brings their own meaning or interpretation to the works that they view. Oh, sure, there are objective aspects of art that can be defined and measures, but these only have to do with the "production quality" of the work, which can be affected by the training and experience of the creator, as well as by technology. An obvious example of technology is how film quality has changed since its inception, with improved filming cameras and techniques, and now computer processing, but even writers may have been subtly affected by the development of the typewriter, and later the word processor and personal computer in how they go about writing novels and stories.
Nonetheless, the meaning and interpretation of a work is largely independent of the technology used to create the work, and rests solely with each individual viewer of the work, and thus is subjective. This goes a long ways towards explaining differences in artistic tastes, not only from person to person, but between different cultures, separated by distance or time. A person growing up in the United States will be familiar with various pop music icons like Elvis or the Beatles, while a person growing up in India may be more familiar with their own native ragas than with Elvis.
But these environmental and cultural influences are only tendencies towards certain influences and styles--people are still individuals capable of choice and change. If your parents listened to country music while you were growing up, you may have rebelled as a teen and listened to rock, instead. But even if you did, you might still find that as an adult you like country music. Or you may have encountered jazz or classical as you got older and decided that you liked those styles of music instead of, or in addition to, country and rock. In any case, it's a sure bet that you wouldn't like Indian ragas if they were unavailable to you and you had never heard them.
One thing I find interesting is how variable this attribution of meaning can be even within the same person. If you're tired or ill, you may find it more difficult to enjoy even a favorite novel, movie, or song than if you were well-rested and focusing on the work. Or you may find new meaning upon repeated viewings/readings/listenings of the work. Having supplemental or background material about the work and creator may also influence how you view the work. That's one of the reasons I like the special features that are often included with dvds. I like seeing things like how the movie was made, or what the producer/director or principal actors thought about the movie they made.
There also seems to be a degree of interactivity that can be brought to bear upon the work. What was the Russian author Fyodor Dostoyevsky really trying to show the reader in The Brothers Karamazov? What was its theme? When Randy Newman wrote the song "Short People", was he really trying to offend short people, or was he trying to highlight the bigotry of not liking short people? In the science fiction movie "Total Recall" (either version, they're quite similar in regards to the plot), is the main character Douglas Quaid really a deep-cover secret agent, or is his espionage adventure just an implanted dream or memory? These are the types of questions each individual has to think about and decide for themselves.
Even the medium can affect the degree of interactivity. When reading a prose story, the author can describe characters and settings, but it still requires the reader to imagine what things look like, and how certain things described in the story actually work. With film, actors, props, and settings are all visible to the viewer, so less imagination is necessary. Still, a good movie like "The Matrix", "Inception", or the previously mentioned "Total Recall" can make the viewer question if what he is seeing is "real" or not.
This idea of subjective interactivity can also be brought to bear upon non-fiction, or even upon reality itself. When reading an account of a scientific event, for example, you have to know enough science and the terms they use to understand what the article or account is telling you. When watching or reading a news story, you have to understand if they are reporting facts for you to interpret, or if they are merely giving you a second-hand account or interpretation of the events. Is that National Enquirer headline really reporting the fact that Elvis is alive and living incognito in North Dakota, or are they merely reporting that someone else is saying that Elvis is alive, without sufficient evidence of their assertion? Is history really a set of facts written down? Or is it a set of facts that the historian deemed as important, and thus ignoring the rest of the available facts? Or is it even just the historian's interpretation of a set of facts, and not the facts themselves? Again, just like fiction, the individual has to bring their own understanding and interpretation to bear upon what is presented to them.
And isn't that how reality itself works? Your senses perceive raw data, such as the light that reaches your eyes, and your mind interprets that data to tell you what you've seen. Thus, reality itself may indeed be quite objective, but our perception of reality is subject to how we interpret the data of reality, the meaning that we individuals ascribe to our circumstances and situations.
What is the difference between fiction and nonfiction, then? Fiction could be said to be an attempt to create meaning by describing a set of facts or events, while nonfiction attempts to find meaning by discovering and interpreting a set of facts or events.
And now I believe I've strayed far from my original starting point. I suppose I should be providing my grand conclusion or thesis at this point, but I don't really have one. I've presented my interpretation of various facts, tried to see if there's a connection or relationship between them, and I now leave it up to you to come up with the conclusion to be derived from it.