The standard wisdom regarding Milton's Paradise Lost goes something like this: Sure, Milton may have been a devout Protestant Christian, but his writing subverts his faith. William Blake's critique - that Milton wrote better of Satan than of God because Milton was of Satan's party without knowing it - was correct. In retrospect we can see that Milton's Satan captured his readers' imagination more than Milton's God, leading to exactly the opposite effect than that which Milton intended.
To be fair, there's a lot to support this suggestion. After all, Milton was intimately tied to the more radical of Protestant sects still in rebellion against the Catholic Church, and he famously rebelled against Charles I and the Anglican bishops in support of Oliver Cromwell. So if Milton rebelled, and if Milton's Satan rebels - then they must be the same... or so goes the party line. But before you buy it, you might want to consider Peter Saccio's suggestion:
Now Milton admired heroic, defiant individualism... that admiration helped him to create the striking energy of Satan, and Blake was right to detect a vital current linking Milton and his devil. But that does not mean Milton was of the devil's party. Heroic defiance of itself is neither good nor evil, it is a quality necessary to sustain either good or evil. It's moral value depends upon the cause in which it is enlisted. It was a quality Milton knew well, but he can distinguish between Satan's cause which is personal alienation, envy, ambition revenge; and loyalty to the truth.Man do I love the Teaching Company.
In the poem there is another solitary figure which opposes the devil and his angel, the Seraph Abdiel."Then whom none with more zeal adored the deity and divine commands obeyed, stood up, and in a flame of zeal he spoke, 'Oh argument blasphemous false and proud... Shalt thou give Law to God?"Abdiel goes on to rip Satan's pretense for rebellion to logical shreds. And there is your virtuous, individual, defiant Protestant.