Good Vs. Evil

I just finished the new Harry Potter book. It was much like the other ones, which is to say, an easy read, but for some reason strangly engaging. So many of these fantasy/sci-fi stories all have the same basis; a fight between good and evil. Star Wars had the light and dark sides of the force, Lord of the Rings had Frodo trying to destroy Sarun, and Harry Potter has Harry fighting against Voldermort. People love these stories, love this fight between good and evil, but it hardly seems realistic. I mean, where in the real world do you see such a clear distinction, where it is so obvious which side you should be on. Maybe that's why people like these stories. It's very easy to see that Darth Vader, or Voldermort is evil, and should be fought. There would be plenty of people willing to fight, and die, to eradicate such people from the planet, because anything that opposes them must be good. But unfortunately in the real world you have to choose between the lesser of two evils, you have to decide where you are going to stand, even if you're not completely happy about it. I think that's what people like about religion so much, it certainly was something I liked about it. God was obviously good, Satan obviously evil, thus it was easy to say that I was willing to live for God, and if neccessary, die for Him, because I knew that I would be giving my life for something good. But in this world....what's there to die for? Maybe some friends or family, but not so much becasue they are "good" but because you love them. It makes me wonder, if there is no cause worth dying for, is there any cause worth living for? That is a question I'm sure many people have asked, and I for one haven't found an answer yet.