If you define good as a very popular movie, or if you define good as in profitability, then, yes, the Transformers movies are unimpeachably good. Because they made oceans of money.
The problem arises from the fact that whether a movie is actually good, as defined by a quality point of view (I.E: Coherent Script, No Plot Holes, Well Developed characters, good actors, etc...), or it's a good movie as defined by popularity and profitability, is poorly defined in the media. We see movies like Transformers getting good reviews, while other, much more well written movies get bashed on. The problem, is that there's no clear cut definition of a good or bad movie. It's subjective enough so that vastly different movies can be called good, for entirely different reasons.
And it applies to written media, as well. Twilight sucks ass. But it's popular, and profitable. So is 50 Shades of Grey (Or whatever it is called).
Game of Thrones is good, AND it's popular. But it took a LOT of time for it to be recognized by the public at large. Because it doesn't actually appealed to the collective public's tastes at the time it was launched, and it had to "wait" until the time was right for it to really get popular. After Lord of the Rings and Harry Potter made such huge successes on screen, the time came for game of thrones, a more realistic fantasy, to get the favor of the audience at large.
The simple fact is, most people are dumb, or at least have a respectable amount of willful disbelief. Enough so, that movies don't have to have a GOOD script, but only actually have to LOOK good and IMPRESSIVE. There's also the fact that many "Transformers" type movies are oriented towards the ages of 7-16 years, where most of the time, the child/adolescent doesn't go to the movie aloe, but brings his parent's/friends along. Which in turn brings "artificial" revenue, since at least *some* of the people going to watch the movie didn't actually WANT to see the movie, but got dragged along.
Now, when a more perceptive individual who doesn't have all that willing disbelief when watching a movie actually goes and watch it, his mind instantly recognizes the flaws the others either don't notice because they're dumb, or 'forgive' because, hey, explosions, it's fun.
Proof of Concept: Twilight.
For years, Hollywood was riding the Vampire train like there was no tomorrow. From actual quality movies like Interview with a Vampire to gag comedies like Dracula 2000, there was a neverending stream of vampire movies... Action ones like Blade and Ultraviolet & Underworld... Drama ones, etc... This embedded the collective youth mind with the fascination with the Vampire subculture, and made it mainstream.
That collective youth, dumb and fed hollywood bullshit by the handful from the cradle, had absolutely no criteria whatsoever, and thought Vampires were cool. Now comes Twilight, which introduces a NEW type of Vampire, one that was NEVER EVER seen before. And that appeals to the very same slash fanfic subculture of such dregs as to make anyone with half a brain sick. And it introduces a female protagonist which perfectly represents the stereotype of the angsty teen female. BAM! Instant hit.
Not minding the plot holes, bad writing, bad character developments, the collective youth embraced it and it was made popular, and by extension "good" as far as the media is concerned.
So yeah. Because youngsters don't actually read good fiction, they get impressed with whatever shit is tossed their way.
Of course, as the Game of Thrones example shows, this can work in a positive manner, too, introducing actually good fiction to people who otherwise wouldn't have ever heard of it.
