At the Oscars last night the movie "Milk" won for best screenplay and Sean Penn won for best actor. Heath Ledger won for best supporting actor as the Joker in "Dark Night."
Here's my issue: the academy doesn't want to recognize truly great work, they want to recognize what is popular. I haven't seen "Milk" so I can't really judge whether the performance was that as good as they say. However, it is my opinion that the win had a lot more to do with the subject matter of the movie than with the actual performance (I call this the "Brokeback effect").
Additionally, Heath Ledger had to win for playing the Joker. Since he died there was no other option. I genuinely think he did an amazing job in playing the Joker, but no one else had a chance of winning because they didn't die. Now they can't be upset that they lost otherwise they will be jerks, and they can never know if their performance was the best or not (because they didn't die).