The most important component for any story is tension - the feeling surrounding any potential loss or failure. As more and more is at stake, the more the tension builds. And, of course, what activates tension more than conflict? When two or more sides collide, there's always the potential for losses. All the classics have this incorporated into their words - a story where something is at stake, from a relationship to someone's life to the fate of the world. Let's face it: Readers eat that stuff up.
However, just for fun, what if we muddy the waters a little? Do we still root for the main character if the family they are protecting is a violent organized crime family? What about a family of terrorists? How do we feel about a main character fighting for his country, which just happens to be Hitler's Germany? What if the only way to defend the innocent is to unleash a terrible weapon upon other people, some of whom are just as innocent? (Yes, I recently saw Oppenheimer) Now things get rolling. Now the tension rises. Why? Not only do we have the greater conflict - trying to do what needs to be done - but we have an internal conflict of whether the character should take on this task, and also whether or not these characters can spare themselves from possibly doing the wrong thing entirely; that is, if we even understand what the wrong thing is.
This is where simple conflict becomes writing in shades of gray (no, not that shades of gray) and offering the reader more than a story, but asking them a question. These are stories where we have to think first not about what is actually right or wrong, but the validity of both sides of the argument. When both sides have a good point, or when both sides have moral flaws, the reader is not only taking in the story, but hopefully they are thinking about just what they might do. The reader has engaged not only with the story but with the ideas. And, as I have said countless times, when the writer gets the reader to engage with the words, it's always a win.
This isn't as difficult as it may seem. There are plenty of topics that feed into the shades of gray, and they are still effective: vigilante justice, social obligations, personal freedoms, cultural conflict - that's just a sampling from a pretty huge list. As an exercise, I suggest taking any subject where the answer isn't so simple, and just writing a story about a person thinking about both sides of the argument. It doesn't have to be a story, just let the character explore the different ideas at hand. If you do this for a bit, a story will come to mind about whatever tricky situation you choose. And if you write it in shades of gray, you can draw in the reader.