For me, it's a tie between Harry Turtledove and Naomi Novik. From page 1 of all thier books, I knew I was reading the works of master story-tellers.
I highly recomend the Worldwar and Colonization series, (Turtledove) as well as His Majesty's Dragon and Throne of Jade. (Novik)
Yup, Harry Turtledove would be my #1...just.
The World War/Colonization/Homeward Bound books are great, i just finished re-reading them.
Clive Cussler and Tom Clancy would be next on my list.