Wikipedia's entry for Imagination begins thus...
Imagination is the ability to form mental images, or the ability to spontaneously generate images within one's own mind. It helps provide meaning to experience and understanding to knowledge; it is a fundamental facility through which people make sense of the world, and it also plays a key role in the learning process. A basic training for imagination is the listening to storytelling (narrative), in which the exactness of the chosen words is the fundamental factor to 'evoke worlds'.
In my particular example from last night, I think each of us learned a fair amount about the other that might have been extremely difficult to communicate more directly. Given that we were speaking by phone, it was impossible to use any concrete visuals -- such as gestures or facial expressions -- to help articulate impressions and emotions that words alone cannot not adequately describe. But in utilizing our imaginations, we were able to express more complicated ideas via a sort of proxy.
It should come as no shock that comic book creators frequently and repeatedly need to use their imaginations to develop the stories they do. They are, in effect, trying to communicate a set of ideas from their brain to ours, and they use the comic book story as a more easily digestible metaphor. Some of the ideas are simpler: Good triumphs over evil. But some ideas don't boil down quite so easily. Would Alan Moore have been as effective, do you suppose, if he said, "Hey, comic characters don't have to be this two-dimensional garbage that we've been reading for decades" instead of writing Watchmen? The larger metaphor was able to capture our collective imagination, and the ideas he presented there have been swirling around people's head for over 20 years now.
How about Steve Gerber? He could have simply said, "Hey, publishers shouldn't treat their creative freelancers like crap." But by bringing Howard the Duck (and his cousin Destroyer Duck) into the argument, he's placed more concrete images into our heads. He deliberately spoke to our imaginations, knowing that a more rational approach using logic wouldn't be as effective. (Not that Steve didn't do that, too, but it didn't "take" as well as the more imaginative imagery he conjured up.
His imagination is one of the greatest reasons I have so much admiration and respect for Jack Kirby. His illustration skills weren't the best, but his neurons were firing full-blast all the time. He could develop whole universes in the blink of an eye. He could start a story not knowing where it was going to end up because he knew he'd think of something by the time he got to a point where he needed it. He could throw away brilliant ideas casually because there was never a question that another one would hit any second now. And it was a lack of respect for those imaginative powers that led Jack to leave Stan Lee in the first place. And it wasn't just limited to storytelling itself -- how many times did he single-handedly revolutionize the entire industry? Jack wasn't a great comic book creator because he could draw good stories; Jack was a great comic book creator because he threw literally thousands of incredible ideas and concepts out to the world via his work.
So, for as much as you might appreciate the writing of a Warren Ellis or an Ed Brubaker, or the artwork of an Alex Ross or a John Cassaday, their greatest talents are not so much that they can write or draw well; rather, it's that they can effectively present their imaginations to you.