In discussions of Art, people use the would "quality" in several different ways (probably more ways than I'm about to list), and then create confusion by using the word in conversation without being clear what they mean by it.
By quality, some people mean a ranking system for what they, personally, like and dislike.
Others are speaking about the likes and dislikes of an elite class, critics, to which they may or may not belong.
Still others are talking about economic power -- how much money the work has generated. (People will often claim they are not talking about this when they are. They will claim that they are talking about how many people LIKE a work, but they gather their statistics by tallying how many copies of said work have sold, which isn't necessarily the same thing. People sometimes buy things they don't like, i.e. for status or to read/see/listen-to what everyone else is reading/seeing/listening-to).
Some people use "quality" to mean "influence," and by this measure, a work has high quality if it has inspired other works or trends. Note that a work judged bad by other standards can still influence. And a works influence is not always good. (Example: "Lord of the Rings" has been so influential that it has inspired a whole genre of similar works. How many of these spin-offs is any good?)
Some people simply mean lasting power. To them, if we're still reading something that was written several hundred years (or some other arbitrarily long period of time) ago, it has quality. Some people say a work has quality if it conforms to certain standards -- standards which have usually been laid down by critics (for instance, at one point in history, dramatic critics decided that all plays had to take place in real-time, so that if the play was two-hours long, it could only cover a two hour period).
Of course, many people define quality as a combination of these things and still more use it as a fuzzy term, not quite sure what it means, but with a general feel of "I like it and a bunch of other people seem to like it too."
John and Jane have no basis for conversation if, when they speak of "quality," John is talking about influence and Jane is talking about whether or not she personally likes something. Alas, they will probably converse anyway.
People get really confused about whether qualitative judgments are objective or subjective. This confusion stems from a much larger confusion: are people individuals or members of a group? In other words, can an artist create a work that affects our general human nature or must he try (and often fail) to appeal to each person individually?
The answer to whether we are individuals or herd animals is simple: we're both. We're herd animals with individual differences. But this is too complicated for most people, and throughout history, people have tried to deny it and flip the personality-coin to either heads or tails. In reality, it is forever wavering between heads and tails.
People are based on shared genetic code. We all start out with the same code. (Or do we? Some people have mutations not shared by others. We all start out with SIMILAR code. It's not exactly the same). Then, our life experiences -- upbringing, books we read, etc. -- changes us into individuals. Which means you will always be different from me, even though we are members of the same herd.
The mind is incredibly plastic. On the other hand, it's not completely plastic. The are some aspects of the mind that are the same in most people. Artists can try to appeal to these parts. If they appeal to the plastic parts, they will create works that appeal to some people and not others.
Neurologist V.S. Ramachandran has been studying art and the human brain. He seems to have uncovered certain patterns that artists can use, which, in general, cause certain effects in normal human minds. Interesting stuff.
I believe that the most useful way to view art is to simply ask, "Do I like it?" "Does it move me?" "Does it change me?" "Does it entertain me?" Why seek out art if you're not trying to be moved, changed or entertained?
Well, there are other reasons. Many people seek out art in order to seem more intelligent. They read, say, Camus, not because they want to, but because they think people will be impressed. Others read certain works because they think these works are good for them. They read, say, "King Lear," not because they want to, but because they've been told that they won't be a complete person without having read it.
I'm not a big fan of these reasons to seek out art. But I don't mind them if people are honest with themselves and each other about them. I'm deeply saddened when (as so often happens), a friend sees a movie or reads a book and says, "I don't know if I like it or not." This friend is letting other people's judgment -- or personal desire to look smart -- to interfere with their natural feelings and thoughts. Most likely, this friend went to SCHOOL. School is where many people sustain damage to their thoughts and feelings. It's where authority figures (professors and other students) tell you what is good and what is bad. It's a rare (but wonderful) school that helps you grow into a person who feels and things deeply for yourself. Most schools just say, "look, we know you're in a hurry, so we'll tell you what's good and bad and let you get on with your life." Beware these schools. They are killing small parts of you.
You DO know if you like something or not. You MUST have some feeling when you read it or watch it. Did it bore you? Did it move you? Did it make you laugh or cry? When people say they don't know if they like a work or not, they generally mean "I didn't like it, but I have a feeling it's a Great Work, and I'll look like an ass if I admit I didn't like it." Or they mean the reverse: "I have a feeling this is generally considered bad, but I actually enjoyed it, and I don't want people to think I'm stupid." Of course, they might also mean they liked parts of it and didn't like other parts. Which they should say. A book CAN have a good first chapter and a lousy second chapter.
(Sometimes -- rarely -- a person means, "I didn't like it, but I have a feeling I MIGHT like it if I studied up a bit and read it again." This feeling might be worth listening to. More below.)
So is it okay to say a work has "quality" if I like it and that it doesn't if I dislike it? Yes. But I would add some advice, which you should only follow if you wish to. The reason to follow it is that they might lead to a richer life: a life in which more works move you or a life in which you might be moved more deeply by works you already know. But you should STOP following this advice if it interferes with your subjective quality gauge. The most important aspect of art -- for YOU -- is they way in which it moves you. So if you find yourself being moved less (if you start saying, "I don't know if I like it"), then STOP following all external gauges. STOP listening to professors and critics. For God's sake, just read and watch and listen! Experiencing art should be like falling in love. Don't marry the girl because your father tells you to! Marry her because you love her!
Having said that, it is worthwhile listening to (some) critics because they can lead you to art you might not know about or be able to find on your own, and this art might move you.
Some art can't be enjoyed (fully) without knowing certain things before you experience it. For instance, you have to understand some archaic words before you can enjoy Shakespeare. A critic may be able to give you this contextual information.
A critic might point out some subtle aspect of the art that you missed when you first experienced it. Knowing about it might totally change the way the work affects your brain, which may make the work move you more deeply.
A critic can point out which works have endured. If a work has been read for centuries, this might be just because an elite group has kept it in the curriculum for centuries. On the other hand, it might be because this book has moved hundreds of thousands of people. And if it has, then there's a good chance that it will move you too, because though your nature is plastic, it's not completely plastic.
I have written about works MOVING you. As humans, we are moved mostly by things that tug at our animal nature. We are moved by surprise, whish hooks into our fight or flight instincts. We are moved by things that make us want to eat or fuck. We are moved by certain patterns that fire our sense-systems. And we're also moved (I believe to a somewhat lesser extent, but still truly moved) by intellectual games (generally by experiencing surprising new thoughts).
Critics (especially academic critics) often tell us that a work is good (or bad) for all sorts of obscure reasons. And they make us feel stupid if we like a work because it scared us or because we fell in love with the heroine. We're taught that these are the effects of "entertainment," not "art." Yet these are the things that appeal to the deepest part of who we are. Look for those works that make you hungry, that turn you on. Look for those works that make you say, "what's going to happen next?"
"King Lear" is a great play because it deals, in a deep way, with parents and children, with love and aging and fear of death. It deals with all of these simple, eternal aspects of being human. "The Brady Bunch" deals with parents and children too. I'm not saying "The Brady Bunch" is as-good-as "King Lear." My internal quality gauge tells me that "The Brandy Bunch" is trash, whereas "King Lear" is a masterpiece. But "King Lear's" lofty status doesn't stem from the fact that it deals with obscure, highly-intellectual, philosophical truths. "King Lear" is great because it's a well-told tale which deals with simple human truths. Whereas "The Brady Bunch" is a poorly told tale which deals with simple human truths.
By well-told and poorly-told, I'm talking about technique: world-choice, avoidance (or non-avoidance) of cliche, etc. But these stylistic concerns are important because they allow me to FEEL more deeply. They have a greater (or in the case of "The Brady Bunch") a lesser chance of hooking into my human nature and moving me.
But what if you're not moved? If you read "Hamlet" and are bored by it, should you say it's bad? I think you should first note than many people think it's a great work. You might want to investigate why they think so and if there is any prep work they had to do before reading it (i.e. learning what certain words mean) in order for the work to move them. If you follow their advice and are still bored, then yes, you can say it's bad. Your subjective judgment must ultimately trump all other judgments, because the most important aspect of art for any person must be the effect art has on that person.
(Note that as a culture, we are flooded by information and must discard some of it. Our libraries aren't big enough to contain all works and our lists of 100 best movies can, by definition, only contain 100 movies. So we must use odd means of choosing what to preserve and what to discard. We can't consult every person on Earth when a decision has to be made. Since these choices are made in a practical (but imperfect) way, they should be taken with a grain of salt. Just because a book is or isn't in the library, we can't say that book is good or bad. We can only say it's good or bad if we like or dislike it.)
"Quality" is best used as tool. Don't use it to place works on some cosmic scale. There is no cosmic scale. Use rankings as a way of finding works. If a NY Times critic says, "go see this film; it's the best film to come out in the last 10 years," then you might want to see the film (especially if that critic has steered you right in the past). But if you see the film and dislike it, don't say, "I didn't like it, but I know it's a good film." Please, please, please don't sell your soul. Be brave. Say it was bad.