Excerpt from Alan Moore's interview at Wired:
One thing is that with the comics medium, it has been proven—I believe by Pentagon tests in the late '80s—that comics are actually the best medium for imparting information to somebody in a form that they will retain and remember. That's not just me saying that, that's the Pentagon. I personally feel—and this is just pseudo-scientific hippie bullshit—I feel this might be because the unit of currency of what used to be called our left brain is the word. Our left brain is what goes about speech and rationality. The unit of currency for our right brain, conversely, would be the image, because the right brain is preverbal.
So perhaps it is because of the combination of words and images in a readable form that comics does have this unique power. Now, of course, movies are a combination of words and images, but they have a completely different structure and completely different way of working. With a movie you are being dragged through the scenario at a relentless 24 frames a second. With a comic book you can dart your eyes back to a previous panel, or you can flip back a couple of pages to check whether there is some reference in the dialog to a scene that happened earlier.
You can also spend as much time as you want absorbing every image. This is especially true of something like Watchmen, where I was trying to take advantage of Dave Gibbons' brilliant capacity as a former surveyor for including incredible amounts of detail in every tiny panel, so we could choreograph every little thing. The little symbols and signs appearing in the background, every little touch could be choreographed to the last detail, and we knew that the audience—because they'd be reading at their own pace—would be able to study each panel and to take in these almost subliminal details. Even the best director in the world, even a person as talented as Terry Gilliam, could not possibly get that amount of information into a few frames of a movie. Even if they did, it would have zipped past far too quickly. Because the audience at the movie theater is not in control of the experience in the same way somebody reading is.
One of my big objections to film as a medium is that it's much too immersive, and I think that it turns us into a population of lazy and unimaginative drones. The absurd lengths that modern cinema and its CGI capabilities will go in order to save the audience the bother of imagining anything themselves is probably having a crippling effect on the mass imagination. You don't have to do anything. With a comic, you're having to do quite a lot. Even though you've got pictures there for you, you're having to fill in all the gaps between the panels, you're having to imagine characters voices. You're having to do quite a lot of work. Not quite as much work as with a straight unillustrated book, but you're still going to do quite a lot of work.
And I have to agree. Comics are comics; you read it at your own pace, you analyse the details like it held the secrets of the universe, you enjoy the little hidden things both in the art and story, and you fill in the gaps. That's what makes it great, and that's why, no matter how well the movie is done, the comic will always be better.
(Well. In normal circumstances at least. I've seen mediocre books or short stories become great movies, but that's a separate story altogether, and to date I haven't seen it done with comics yet.)
On the other hand, I think dismissing the flick like he does is a waste of good entertainment as well. Time to quote from Dave Gibbons' interview in the same issue:
The most bizarre thing was to actually be inside the Owlship, you know? As I kind of implied in an earlier answer I've always loved drawings and measured plans of things. I went to a lot of trouble to make the Owlship convincing and make room for everything that we saw inside it. So, to actually be inside this thing—the thing that had been inside my head, I was now inside that. It felt exactly like the space that I'd felt when I'd done the drawings. I think that was really the strangest thing, to sit in the command chair and play with the joystick and press the buttons and watch all the lights flash on.
And that's where the magic really is. That's why those geeky movies are so great. It's like, well, going to a theme park, except usually with higher quality results. These things have lived in our imaginations for years, and now we get to see them there, big and real-looking. It's, well, fun.
Another important thing missed there is that movies can be a social experience. Comics, by the very merit of being read at your own pace, are solitary; you can get together with people to read comics, but you don't actually read together — well, you can, but it kind of ruins the experience. That's what is (well, used to be) so great about Heroes; it's kind of like reading a comic book, only I do it with my girlfriend, and we react together.
Short version? Absolutely do go watch the Watchmen, but not if you haven't read the comic yet. :-)