I agree that Revolutionary Road should be in there. It's not a masterpiece, but DiCaprio was simply amazing in this movie (just like Kate Winslet). Anyway I'll vote for the movie I liked the most in this list: The Departed
Leonardo is indeed brilliant. I always kinda didn't want to jump on the Leonardo bandwagon, in fear that people were only loving him because of typical Hollywood hype. But he is actually totally amazing in all the roles he plays. I loved him the most in: