For me, Writing is a religion. There's something pure, clean, almost holy about the mystical way the words come into my head, the characters appear, the plot surfaces, as I tell the story. I love the wonder and mystery of the process, the way the characters take on lives of their own and change the story, the way I sometimes write myself into corners, only to have a way out magically appear in my mind after letting it simmer for a few days (a technique that often serves me well in real life as well).
I love using the language, creating the flow of narrative, the syncopation of dialogue. I view it as writing Music, as surely as any composer. I see things very cinematically in my head, and do my best to transfer that immediacy to the page.
I believe a writer should tell themselves a story they'd like to hear, under the assumption that their enthusiasm will be infectious. I think writing with the motivation of "my readers will love this" is an express ticket to mediocrity. Obviously, you do have to temper subject matter with common sense and a certain degree of intuition regarding marketability (No matter how passionately a writer may feel about croutons, there's a pretty good chance the reading public will not be getting on board for a sprawling historical novel on the subject), but this does not preclude you from telling the story you want to tell without compromising your principles or selling your soul.
As for my own stuff, I want it to be kind of an assault. I want it to grab you by the shoulders and shake you up a little (or maybe a lot). I want it to be passionate, be it through Cloud 9 romance, laugh-out-loud humor, cold-blooded murder, or delicious eroticism. I want to embrace the Human experience as best I can and share what I know, what I think, what I feel and what I dream.
First and foremost, however, I want to entertain (which is not nearly as superficial a goal as one might think). All my lofty ambitions to change the world through my writing won't do me or anyone else the slightest bit of good if no one's reading the work. My responsibility as a storyteller is to captivate you, to deliver that moment of religion where you decide, "I'm in," whether you're reading one of my essays or a story of the fantastic. If you get something more profound out of it in the process, then I've done my job exceedingly well.