Good thread. A few thoughts...
I lived in Alaska for years. What many posters here do not seem to know is that much of Alaska is flat, boggy and REALLY buggy. Much of Alaska is high peaks that are not runnable. You would never want to run any long stretch of backcountry in Alaska. It would be miserable. The roads are also few and are overrun by campers in the summer time.
Although Maine is beautiful, much of it is similar to Alaska with bugs and wetlands. Running up the coast of Maine would be beautiful (perhaps wet) if you could do it in an off-season like April/May, or late October.
My choice would be Vermont. Vermont has 5000 miles of rural paved roads and 7000 miles of dirt roads. Running the dirt is amazing and traffic free. There are hills, mountains, rivers, lakes and great scenery. There are also many very small New England towns with one general store, a library, church, inn and a gas station. Makes for easy stopping for a drink or food or lodging.
Peace.