Alfred the Great
is the only English monarch to have earned the soubriquet "the Great". Indeed, there are only a select few figures in the whole of human history to be so called; Alexander, Genghis Khan, Charlemagne, Catherine of Russia... and Alfred.
His recovery from the desperation of Athelney to the victory of Edington is one element of his greatness - but there's much more to Alfred.
His diplomacy - both with the Danes and with other Saxon leaders - was masterly. The Danes never actually left England - Alfred's forces were never strong enough to force them out - but Alfred was able to negotiate a division of England (along the line of Watling Street) giving the Danes control of the North-Eastern half - the Danelaw.
Alfred also established a widespread system of defence for this new "country" of England; he had a network of garrison towns (burhs) across his realm, so that any future invader could never win the swift victory which nearly fell to Guthrum's Danes. He founded a navy.
Alfred gave the English their first common code of law. He drew from several existing sources and collated them into a single document, which could be referred to anywhere in his realm.
He gave the English a body of literature - causing a number of key Latin documents to be translated into Anglo-Saxon (things like Bede's Ecclesiastical History and Boethius' Consolation of Philosophy).
He added to these translations two important new works - the Anglo-Saxon Chronicle, which detailed the history of Alfred's predecessors, and a Life of Alfred - from which most of our knowledge of these events comes.
It's worth noting that Alfred himself was illiterate, until the age of 38 (long after the events of Athelney and Edington).Perhaps, to a cynical modern age, it may be these two pieces of "history" (or propaganda) to which Alfred owes his fame. Modern historians certainly delight in picking holes in the incidents reported in these works.
It is generally acknowledged that the Life of Alfred was actually written by the welsh bishop, Asser. Some believe he also wrote the Anglo-Saxon Chronicle. We know that he was heavily involved in the translations Alfred published.
Nonetheless, Alfred does seem to have been a truly remarkable man. It is true that his efforts would have meant little if he hadn't been followed by other remarkable men - not least his grandson Athelstan. But, without Alfred, Athelstan would have grown up a Danish slave.