Morgoth, of course, represents
Satan, to
Sauron's
Beelzebub. A comparison of the opening sections of
The Silmarillion with
Paradise Lost is quite instructive. Despite Tolkein's Morgoth being motivated by a more creative form of vanity than
Milton's Satan, he still makes the more unpleasant villain. Milton presumably fails to make
God sufficiently appealing as an alternative.
IMHO.