Absolutely characters for me. If a game has an interesting narrative but bland characters I will quit after a few minutes. On the other hand, if the characters are interesting, I'll play through hundreds of hours of a garbage narrative for them. My favorite kind of games are actually those that have almost no larger narrative to speak of, but rather focus on smaller, more intimate moments between the cast. That's pretty rare (especially in RPGs), but Dragon Age II, The Last of Us: Left Behind, and Gone Home are each pretty good examples.