I don't think it's really possible to vote on this truthfully. In just about anything with a half-decent story, it's due to the presence of drama. Perhaps I've overseen something, but my point is that other elements all incorporate drama. From there, you could roughly branch things into fantasy, sci-fi, horror, comedy, romance or action. Even now, the genres can very easily overlap each other. Fantasy, being about the presence of magic, can be found in any of the others. Sci-fi and horror go hand-in-hand commonly. Elements of comedy can be incorporated into anything. And so on...
If you say you're after which element people prefer, that's a better way to put it, because it's an easier term to relate to. An entire genre simply isn't specific enough.
Tl;dr: I don't think genres are specific enough to determine what people like in an anime. Specific elements are better.
I'll say that if "slice of life" and "mecha" are legit elements, I'll go with "underworld" as my number one.
