Of the films I had seen in the Best Picture category, I would have rated District 9 significantly higher. The story wasn't one we'd seen variants of thirty-seven times before, and the main character wasn't charismatic or likeable. That's a brave movie-making choice right there.
As for people complaining about Bigelow winning Best Director, and them saying she only won because she's a woman, here's a can of shut-the-fuck-up, drink deep.
She won in spite of being a woman. If you can't accept that little fact, you're part of the problem.