I've gotta say that I think GL's most underrated album is Salute.
It's my (current) favorite, and has wonderful melodies like "Biscuit City" and "Romance" on it which are two of my favorites.
This album is also more 'electric' than most of his others, and his voice was still in fine form (unlike on A Painter Passing Through).
I guess I like this album so much also because it contains no overtly 'country' songs on it!
Just a really great, underrated album all around.