It's a little hard to get to the heart of why THE LEGO MOVIE works without getting into some really huge spoilers about the final act. As always, consider this your warning that if you read this before seeing the film, plot secrets will be present in this review.
"They just made the movie to make money" has to be one of the most ignorant criticisms laid on any film. It's not as if mulch-national corporations are in the business of staking a massive sum of wealth on an investment that isn't likely to pay off. That's not to say that there aren't films made as cynical cash-grabs. (I've been a bystander to a few of these in my time in the industry. Sometimes they work. Sometimes they don't.) It's not that I don't understand the gut impulse to dismiss THE LEGO MOVIE as such, but I do think it's important to recognize how close-minded that assertion can be.
I can't help but think of He-Man, which was one of the first toy-to-cartoon franchises. When you delve into the history of the series, you're left with what appears to be a pretty clear-cut case of "We have these toys, now let's make a show to market them so the kids will be interested in buying them." It's afternoon cartoons as half-hour toy commercials, pretty much the opposite of Bugs, Daffy, Scooby Doo and so on.
So does that mean that this cynical attitude filtered all the way down through every level of He-Man's production? I'll let you be the judge. Take all look at this interview with Michael Halperin, who developed the cartoon show:
Can you tell me some of your work on He-Man?
In 1983, before "Masters" became a series, Mattel had produced the action figures. Once they were on the market, children contacted the company because they were confused. Who were the good guys? Who were the bad guys? Where did they come from?
What was your job?
Mattel asked me to come in and create the back story (bible) for "Masters" that could act as a device for merchandising the figures as well as the premise for the TV series (Filmation had begun the process of designing the cartoon characters -- but they had no stories). I was Creative Consultant to the series during its first year (65 episodes) with the job of approving all story lines. I'm proud to say that I brought Larry DiTillio into the series. His Dungeons and Dragons gaming background proved invaluable as a writer. He was what I looked for in story creation.
What are the main stories you developed?
I developed the story of how Prince Adam became He-Man; the origins of Teela; why Castle Grayskull existed in the first place; the "secret" of Castle Grayskull which I believe has never been revealed; how Queen Marlena arrived on Eternia; the topography and geography of Eternia; Snake Mountain, the abode of Skeletor; the origins of Evil-Lyn, Tri-Klops, and Beastman, etc.
The whole interview is worth a read, but what I want to get at is that no matter what the "money men's" motivation was, Halperin and his staff seem genuinely determined to tell good stories and build a mythology using the toys as a framework. I'd never claim that the He-Man cartoon was high art. Certainly the animation was pretty weak, but the stories were rather solid, especially for a kid's show.
The bottom line is that it's dangerous to assume the motivations of the people putting up money for a creative project speak to the motivations of everyone involved in bringing that project to light. If THE LEGO MOVIE sucked, it wouldn't be because it was based on a toy - it would be because the people writing and directing the film couldn't find anything worth saying with what they were given.
Writer/directors Phil Lord and Chris Miller cleared that hurdle and then some. They found a way into the story that would resonate with audiences on an emotional level. In doing so, they might have produced a film with as much to say about a child's relationship with toys as the Toy Story trilogy. What starts off as a seemingly Saturday-morning-cartoon level plot about the evil Lord Business scheming to destroy Lego World eventually reveals itself as an examination of how adults attempting to preserve their childhood by preserving their toys are losing touch with the whole reason toys exist in the first place.
One truly significant difference between this film and movies like Toy Story and Wreck-It Ralph is that those films built their narrative around entirely original characters as the main leads and used established licensed characters as supporting players and cameos. Since Woody and Buzz weren't plucked from existing toylines, the inception of the project wasn't perceived as quite so naked a cash grab.
For much of its running time, the story's drive is centered on Lego character Emmet as he and his friends attempt to deliver a "Piece of Resistance" to stop Lord Business's plan to freeze every Lego land with with a superglue device. It's fairly standard hero's journey stuff... and then Emmet dives into some kind of dimensional rift and ends up... in our world.
The big twist of the film is that he finds himself in a basement containing several Lego buildings and lands that have been preserved on tables. A young boy plays with his father's toys, ignoring "Do Not Touch" signs. For you see, the father is a collector. To him, his toys are museum pieces to be put on a shelf and left undisturbed, not something to take apart, rebuild and play with. The father is so fixated on preserving his creations as he built them that he starts supergluing pieces together. This drives home the point that Lord Business is the in-universe avatar of the father.
(I admit this raises some questions about the nature of free will in Legoland. The connection between Lord Business and "Dad" is pretty clear, but the "real world" scene also contains a pretty heavy implication that everything in the movie is basically the result of the son playing with the toys. So should we even regard the Lego characters as "real" or is the entire movie little more than the imagination of a child? Perhaps, like the final scenes of St. Elsewhere, this isn't meant to be examined too closely.)
What makes this work is that it's a revelation aimed at two different segments of the audience. The kids presumably identify with the frustration of their collector parents forbidding them from playing with certain vintage toys. Conversely the adults get a bit of a jab right between the eyes, perhaps one that will promote some self-examination.
But the bottom line is that this film actually has something to say. Compare that to BATTLESHIP, which had equally dubious source material. BATTLESHIP failed not because it was based on a child's game, but because nothing in it had any real weight.
So in a broader sense, here's the lesson to you, dear Screenwriter: no matter what your project is, make sure you've got something you're trying to express through it.