This is a touchy subject.  Milton Bradley has acknowledged the fact that
the game is imbalanced by introducing three rules options that weigh a
victory towards the Axis (summarized from the Second Edition Rules):

    - Weapons Development Benefits:  The German player starts with
      Jet Power, and the Japan player starts with Super Subs.
    - Restricted Attack:  The USSR player is not allowed to attack
      until the second turn.
    - No New Complexes:  No new industrial complexes can be bought
      or placed.  Only original complexes can be used.

The second optional rule, Restricted Attack, has been used very
successfully at some game conventions, and many experienced players
swear by it.  Of course it depends on the calibre of the players, but
for an even field it can give the Axis enough of a breathing space to
make some headway before the awesome crushing power of the Allied
production advantage takes hold.

The No New Complexes is very controversial.  William Jockusch
(William.Jockusch@math.lsa.umich.edu) notes that "it keeps the
Japanese from building complexes in mainland Asia, which they
need to do."  Japan suffers far more than the Allies from this
rule.