For Best Lead Actor, they were all good, but I think Sean Penn was amazing in his role of Harvey Milk.
Supporting Actor, well Heath Ledger was surely the best Joker I've seen. Robert Downey Jr. was great his his role in the crazy movie Tropic of Thunder, Josh Brolin was good, Michael Shannon was okay in Revolutionary Road (Leonardo DiCaprio , the lead actor, was better), and we haven't seen Doubt yet but I do like Philip Seymour Hoffman.
Leading Actress, I only saw Kate Winslet in her nominee for The Reader. I do think she is quite a talented actress of our day. I also like Angelina Jolie and we started watching her movie, Changeling, but couldn't seem to get into the story. So after 30 minutes, we switched to "Sunset Boulevard", an excellent classic film from 1950.
For Supporting Actress, I have only seen Vicky Christina Barcelona and Penelope Cruz was quite good in her role of crazy ex-wife. Marissa Tomei looked great and all , but I just wasn't as impressed with the story of The Wrestler.
"I *am* big. It's the *pictures* that got small." Norma Desmond