Light is made to be a villain, but at the same time, it's hard to argue that L is exactly good. Sure, he's trying to catch Light and save lives. At the same time, the morality of his choices easily leads to L receiving the title of anti-hero. Although L is technically supposed to be the good guy, his actions and the actions of those trying to catch Light at all are morally ambiguous more often than not, following the idea that the end justifies the means. I can't recall Near and Mello all that well, but I don't seem to remember them exactly being paragons of good and morality.
To say there is really anything resembling a hero or a "good guy" in Death Note doesn't seem right. No matter who you chose to root for, every party was responsible for the deaths of others and, at best, highly questionable ethics.
