For most of his career, Ford held true to a particular vision of the West and its denizens that obviously had a tremendous appeal - and value - to American audiences who found - and many no doubt who still find - their own values and ideology reflected in the classical Western. Eventually, even Ford found the vision unsustainable, and to my mind his best films are those like The Searchers and Liberty Valance that question much of what he and his fellow myth-makers perpetuated. (Cheyenne Autumn is even more apologetic, but it's "preachy", as Scherp puts it, and offputting.)
His godlike status is undeserved, but there's no denying he was a gifted film-maker (although prone to self-indulgence as the most headstrong directors tend to be) and there will always be a place for several of his movies in my collection.
I've never cared much for the cavalry trilogy; they're too sentimental for my tastes, although I admire Fonda's performance in Fort Apache very much.
Two books that helped me greatly in my appreciation of Ford are Jim Kitses' Horizons West - hands down the best book on Westerns that I have ever read - and Joseph's McBride's extensive Ford biography, Searching for John Ford.