I agree with others that "the look and feel of what people like about the comic" is highly subjective and therefore I don't necessarily think Gaiman is onto something. Each character has gone through many variations of over the years from campy to dark to outright weird to some combination of the three to something else I've failed to mention. So who's "look and feel" is the "correct" one in regards to each of the movies?
Well, it's not so much that the comics are somehow "magic." A bad idea or bad execution of a good idea for that matter can be done in any medium.
The thing is... comics are (relatively) cheap to produce. So, we get a lot of content in "comic" form over a long period of time... a movie gets only a couple of hours, on the other hand.
What does that matter? Well, comics (like anything else) change over time. And that change is always a slow, steady move towards what the audience wants... that is, if it's going to continue to be SOLD. Right?
In other words... the comic represents what audiences want because it's had a long, slow "evolution" towards that. The IDEA gets developed more fully, and there's an easier ability to follow what works versus what doesn't.
The comic is better not because it's a comic but because it's got a lot more TRIAL AND ERROR developing it (in most cases). Or, in the case of folks like Moore and his "Watchmen," it's a matter of the guy having the ability to tell his own story with almost no other, conflicting ideas interfering ("many cooks" and all that)... combined with lots of experience with that slow, steady evolution of ideas in OTHER works.
Batman started out one way. He shifted, over time... got "nice" back in the late 1950s (and became boring as a result... and lost market). The 1970s just got WEIRD... but in about 1972, Denny O'Neil and a few other guys changed it all... and gave us "real" characters living in a "real" world again. As much as Frank Miller gets credit for "redefining" Batman, I don't accept that. Everything good about the modern version of Batman came about as a result of O'Neil's "taking it back to the roots" and "treat this as real" sensibilities. You can look at today's Batman and the version that O'Neil started working with in the early 1970s and they're essentially indistinguishable. The only thing he really kept from the 1960's "mod" period was the yellow oval.