I chose "friendship". I prefer stories where the main characters become close friends, especially when they come from different backgrounds, classes, ideals, etc. If some romance pops up here and there, that's fine--it's only natural for some sexual tension to form in a tight-knight group--but I think it should always remain secondary to friendship. It's really easy for romance to get cheesy, so a subtle approach is best.
To use the sitcom Community as an example, the main characters come from all walks of life but eventually end up in the same crappy situation. Their shared experiences cause them to become close friends and, since none of them have a great family life, they form a surrogate family for each other. Sexual/romantic tension does crop up, but it's usually just to drive the story along and almost never leads to anything serious. The core of the story is that friendships and familial ties can form in unlikely places, which I think is endearing without being too corny. I really enjoy that kind of story and would much rather see that in any given medium--television, film, video game, whatever--than the whole star-crossed Romeo and Juliet stuff.