http://www.youtube.com/watch?v=7bbaRyDLMvA
I can honestly say I've never seen someone like this on television who can be so funny yet absolutely serious and eloquentely moving on certain subjects. He almost won an Emmy because he decided to give an eulogy to his father instead of his usual comic monologue once. His 9/11 monologue was fantastic also.
For me, this guy blows every other late-night host out of the water. It's an amazing amount of honesty without pretentiousnous and an utterly intentional aversion to any sort of preachyness whatsoever.
Even if you catch him on normal nights, his monologue is amazing compared to the others who just string random jokes together. His monologue is always about 12-15 minutes long and absolutely continuous. It's amazing what a storyteller he is.