Unless you have lived for a few years in each state, its going to be really tough to define 'best'.
Every state has good things about it.
Every state has some bad things about it.
I think I will choose to define 'best' as the state which you will eventually retire to. And in that case my choice will be where I was born, in Arkansas.
Pros:
Gets all 4 seasons well defined.
Cheap cost of living.
Lots of lakes, with outdoors type of things to do (fishing, hunting).
Friendly people.
Centrally located, so trips to places like Memphis, New Orleans, Dallas, or St. Louis, are fairly easy to accomplish.
Less crime than large urban areas.
Cons.
Very hot w/high humidity in the summer.
Bugs (mosquitos, etc.)
rural living might be considered boring by some (but thats why we now have the internet right?).
more limited choices (shopping malls, dining and entertainment) in comparison to larger urban areas.