Why is Milton's Satan so much more interesting than his Adam, Eve or God?

Good question - well done for not disowning your intuitions about Satan. In a sense, this is the core question that faces readers of Paradise Lost today. Why would Milton, writing a Protestant tract about the evils of monarchism and papacy, have chosen to portray his Satan with all the glamour of a Bond villain, the complexity of a tragic hero, and the 'interiority' - a narrative technique through which we gain access to a character's innermost thoughts and feelings - of our own daydreams? Look at how dynamic Satan is, compared with Adam and Eve, always lolling around feeling sorry for themselves - he is poised on the threshold, he is moving through Heaven and Earth and Chaos, he never knows which way to turn. Look also at his syntax - the way Milton arranges his words within the sentences and poetic structure. Adam and Eve speak in nice little nuggets of wisdom that often fill out the beats of the pentameter quite neatly; there is something fake and unconvincing about this kind of speech, the kind that led Virginia Woolf to accuse Milton of having no knowledge of the human heart. Satan's syntax, in comparison, is serpentine. Much like ours, his speech cannot be crammed into rhyme or meter; it constantly spills out over the strict lines, and is led more by desire than by a fidelity to 'truth'. For another perspective on the unconvincingness of Milton's 'good' characters, have a look at William Empson's critique of Milton's God, a rather high-brow, inaccessible character who speaks with more clarity than feeling.
This is also a good question because it spawns lots of other questions about the nature of literature in general, and religious writing in particular. Did Milton choose to portray Satan in such a compassionate light, or was it merely accidental, a slip of the tongue? How do we separate a writer's original intentions from what they ended up producing, and is it important to do so? William Blake thought that Milton was 'a true Poet, and of the Devil's party without knowing it'. Is this 'devilishness' true of all poets? Or perhaps we think Milton was fully conscious of what he was doing, and made Satan into his 3D, larger-than-life self because he understood the complexity of his task, since God's word is too perfect to be fully understood by human ears. Shelley thought that Milton was a 'moral being far superior to his God,' someone 'tortured with compassion and affection for those whom he betrays and ruins'. What do you think? It might help to inquire a little more closely into the nature of 'evil' and 'temptation'. It is true that evil is often weaker than good, as stories throughout history, up to and including Harry Potter, have been keen to show. Poets of Milton's time used lots of allegorical figures like Satan to portray evil, but they tended to be cowardly, stupid and ineffective, illustrations of the weakness of evil, rather than its strength. But anyone who has ever been tempted knows that evil can also be very strong, very seductive. Could it be that Milton is showing us the seductive side of evil, by presenting Satan as somebody 'just like us'? Modern politicians are still using this trap, showing us images of who we are and what we want, only to then exploit our loyalties for personal gain. Could we have fallen into the jaws of Milton's 'politic' art?