I love how Leo went from being a joke to a lot of people in Titanic (Yes, I know he was in What's Eating Gilbert Grape before Titanic, but Titanic was pretty much the first movie most people saw Leo in), to being such a well loved actor by almost everyone.
I think that's pretty much because he has tried his best to distance himself away from the pretty boy persona that was given to him. So, he ended up being really careful with the projects he picks, and instead aligns himself with top name talent (i.e. Chris Nolan, Martin Scorsese, Ridley Scott, etc.). So, that may have something to do with it.