Gee, I had to put in a null vote! The cast is incredible, and I couldn't watch without them, but then, again, without the story, where would the cast be? It's a collaboration. But what it comes down to for me is not action or romance but what I call drama. The moments that grab me are moments such as when Jack comes to save Sydney in "Truth Be Told" and reveals himself as a spy; the hug between Sydney and Irina; when Sydney enters the ducting (instead of Jack) in "The Box" and Jack puts his hand against it, silently expressing the love he can't express to her personally; the agony with which Sydney faces the prospect of testifying against her father (going to cry in Will's arms). Some of these moments contain action (for example, when the family must come together, machine guns in hands, when they must get out of a jam in "The Passage, Part 1"), but the underlying similarity is the potent emotional impact that these characters are experiencing.
Thanks for the poll. Most interesting to think about.