Because it addresses issues which can be considered "right" and "wrong," it might be called a play of morality. However, justice is not fully served in Macbeth. King Duncan, a good and just king, is murdered. Macduff's family is killed by a paranoid Macbeth while he is trying to save his country. Banquo is nothing but loyal to his friend and fellow soldier, yet his skull is crushed by murderers--one of whome may be Macbeth himself. There is no justice for these characters.
The renowned Shakespearean critic Harold Bloom writes, "Macbeth...is ...anything but a Christian tragedy." Macbeth is not a morality play, it is not a play meant to teach lessons in morality. Rather, is presents the tragedy of a man who could have been great had he not let "vaulting ambition" overcome his better qualities.
Of course, as in all quality literature, there are themes that provide lessons in life for the viewer or reader. Such themes in Macbeth are the evil that human ambition can produce, the destructive power of guilt, and the devastation that fear can cause.
I would have to say that justice is served at the end of the play. After all, the bad guys both die, right? I suppose that you could say that Lady Macbeth gets off too easy because she gets to kill herself instead of being killed by someone else. But Macbeth gets killed and he is killed by one of the people that he wronged most gravely. So if you feel that revenge = justice, then justice is served.
Is justice served OR is this "justice" that is meted out merely an excuse for revenge. Banquo clearly sets out to dispense his own justice for the murder of his family and it is down to the audience to decide that this act of revenge is a form of "rough" justice. Shakespeare's audience would probably have regarded such an act of revenge as justice. Malcolm was the ancestor of King James so Shakespeare was making it very clear that Malcolm was a "good" guy - even if he did usurp the throne - so the auther was probably anxious to make sure that the downfall of macbeth was justice (but that's politics!)