#1 River would be The Saint John River in New Brunswick,
#2 the Saint Croix system that flows along the Maine/New Brunswick Border all the way to the Atlamtic Ocean.
These systems offer a Smallmouth Basser every concievable senario, from heavy current winding through granite boulders as big as a house to lazy spawning flats.
Kentucky Lake and Lake Barkley hands down!
I thought it would be neat to find out what river is your favorite to fish? Mine is the Mississippi River. Second would be the Missouri!
Best of Luck!