Pixel Apocalypse posted a list with a couple of good canidates. I think James Wolk would fit pretty well.
Nolan North is my first choice, but I can kind of understand if they cannot use him, although I would like for them to try every avenue to have him remain Drake.
The next two choices I cannot decide between these two:
Seen him in "The Expendables 2" and I couldn't get the Uncharted theme out of my head every time I seen him running and jumping in the bush haha. Even my mother shouted "Nathan Drake!!" when I asked "You know who he looks like?" haha
He also looks a bit like Drake, and has the same wit and personality on screen.
And I think I have found a perfect Sully!
Imagine him with slicked back grey hair and a mustache. He really reminded me of Sully in the movie "Drive" although he never looked like him, just the way he acted on screen really made me think "He would make a great Sully!" He has the sqaure chin like him too, and is about the right age, and can sound quite a bit like him too.