Have you ever noticed how the concepts of "good movie" and "entertaining movie" seem to be completely independent of each other?
It's not even unusual to see movie reviewers on the internet post or say things like "it was quite entertaining; don't get me wrong, it was a bad movie, but I still liked it." (For example, the latest instance of almost exactly this that I have seen was a review of the movie Battleship.) This kind of statement feels completely contradictory to me.
Now, don't get me wrong. There are two kinds of "enjoying a bad movie": Enjoying a movie because it's so bad, and enjoying a movie regardless of it being (allegedly) bad. I'm not talking about the first type of movie here.
Movies like Plan 9 or The Room can be enjoyed because they are so hilariously bad. It's just outright amusing to see, for example, toy flying saucers being dangled from clearly visible fishing lines, an actor who's very clearly not Bela Lugosi trying to pass as him by constantly hiding behind his cape, or the absolutely horrendous amateurish acting of The Room. Those movies become enjoyable because the goofs and bad acting are so unintentionally hilarious in their own right.
But that's not what I'm talking about. Movies like Battleship have too high production values to be this kind of bad. You don't get amused at such a movie because of its bad special effects, goofs or horrendous acting (it doesn't matter what people say, the kind of acting that professional actors deliver in high-budget movies is not that kind of bad.) What these reviewers are saying is that they enjoyed the movie regardless of it being bad, not because.
This seems very contradictory to me. The main goal of a movie is to be entertaining. (Sure, cynically speaking the main goal of a movie is to make money. However, the best way to do that is for the movie to be entertaining, so that people will want to watch it.) If a movie succeeds in being entertaining, then it has succeeded in that goal and thus cannot be classified as a bad movie. (This doesn't mean that all good movies must be entertaining. I'm just saying that if a movie is entertaining, I wouldn't call it bad.)
With movies like Battleship there seems to be an unwritten agreement, a consensus, that "it's a bad movie", and all reviewers and critics (at least the amateur ones) implicitly obey this consensus. Even if the reviewers enjoyed the movie, they must still point out that it was a bad movie, seemingly so that they don't give the impression of disagreeing with the consensus. It doesn't matter if this results in contradictory statements like "it's a bad movie, but I enjoyed it".
The seeming independence of "good movie" and "enjoyable movie" works the other way too: There are many movies which are universally agreed to be great, yet can be really boring. Take, for example, the "Jimi Hendrix" of movies, namely Citizen Kane. (It's "the Jimi Hendrix of movies" because whenever you see a list of best movies of all time, Citizen Kane will always be one of the top ones, in the same way as Jimi Hendrix is and always will be at the top of all "best guitarists of all time" lists. It would be sacrilege to claim that someone else might be a better guitarist than Hendrix.)
Let's face it, Citizen Kane is a quite boring movie. If you intend to have a fun and entertaining evening watching a movie, Citizen Kane would probably be one of the worst possible choices. Even if you just want to watch it to appreciate a good movie, not just to have an entertaining evening, chances are you will still get bored. Yet this is still universally considered one of the best movies ever made, and no serious critic dares claim otherwise, lest his or her reputation as a film critic be seriously damaged. Again, it's good by consensus, and everybody must agree, lest not being taken seriously anymore. It doesn't matter if it bores you to death when you watch it, it's still a good movie.