I started liking him in The Beach, but I think his best work so far was The Departed and Catch Me If You Can. And Django. And Shutter Island. Damnit, and Inception! Seriously, the dude is a killer actor. I just saw Great Gatsby and he kicked ass in that too!
Romeo & Juliet though, God I hated that piece of crap movie. To me it was a horrible artistic decision to have them speak in the same manner as they do in the original work but set it in modern times. It just didn't make sense to me and any shred of believability was sapped away. The only redeeming factor was that Claire Danes is hot. Although back then I really couldn't stand My So Called Life, so that didn't help either. In those days this is how I always pictured her in my head.