Evil is such an opinionated word. It's a useless term that we seem to like applying to things that we just don't personally agree with. People have different beliefs than us? Evil. Different tastes in culture? Oop, they're evil too. I mean, if you think about it, when Europe invaded the Middle-East on one of their many Crusades, their Crusaders were all viewed as heavenly, God-sent warriors on the side of good and righteousness up there with angels and whatever. Yet on the other hand, the warriors defending their homes from these invaders viewed these murderous, raping, plundering lunatics as complete evil.
But, back on topic: Are humans inherently evil? That's a rather loaded question. Humanity as a whole is flawed. Terribly, terribly flawed. There's a lot of greed, bigotry, racism, sexism, hatred, religious zealotry, and otherwise a lot of complete assholes.
However, there are also wonderfully pleasant people who are just there to enjoy their life without getting in anyone else's way, and there are some people who try to make the lives of others better, sometimes at the cost of their own comfort.
And of course there's the middle ground. Good and Evil always has a neutral zone, though people tend to want to deny it. There's people just living their lives day to day, trying to make it to the next one while making some evil decisions, some good ones, all depending on how they personally feel about the situation.