It's all about tone.
It's all about the characters.
It's all about their inner demons.
If your work doesn't have these things, it doesn't matter how intricate the plot is - it will fall flat.
Take a look at how many television series get canceled after only four or five episodes. Why don't they click with the audience?
I use the example of Tera Nova, a series that I waited an entire year and a half for. It was supposed to be Jurassic Park meets Dinotopia meets Stargate, and it didn't turn out that way at all. After the first episode the entire series fell flat because the characters weren't strong or consistent enough to keep the viewers interested in their struggles on Tera Nova. Secondly, the tone was all over the place. Was this supposed to be a family drama? A science fiction action/adventure? A romance? The writers didn't seem to know, and the audience definitely didn't know. I lost interest fast. Add to that the one-dimensional character yanked directly from Spielberg's War of the Worlds (no surprise, since he executive-produced this series) and you have a yawn-fest.
With Ryan Murphy's American Horror Story, you know what you're getting from the very first scene. It's horror. A haunted house. Ominous music. The characters are all struggling with their inner demons - and they are believable. We want to know more about them, and we do! Who didn't want to spend more time with Constance Langdon, the extraordinary Jessica Lange? Who wasn't intrigued by Violet and her romance with the troubled ghost, Tate? I couldn't get enough.
Tone is the veil that lays over everything in the story, tying it together into a cohesive whole. If you can get the tone and your characters right - and consistent, everything else will fall into place.