I'm going to limit my discussion of the topic of "evil" to the only evil that is really meaningful to us as human beings: the evil we can choose to commit. Therefore, in this discussion, I shall define evil as the uniquely human ability to transgress the laws and will of God, as demonstrated in the Judeo-Christian-Islamic creation myth. The reason I have chosen to do this is that it puts into suspension the fundamentally unanswerable question of God's qualities--good, evil, or otherwise. Since the definition of God's qualities, as Shjade points out, is unavoidably subjective, let us simply settle, for the moment, on the somewhat unsatisfactory answer that God's actions, hence the actions of the created world less mankind and Satan, are by nature neither good nor evil in a human sense, since they come from a freedom that is completely different than our own--more on that later. But first, a quick gloss of the Judeo-Christian-Islamic creation mythos:
God creates Adam and Eve, and all is good. The snake, generally portrayed as possessed by or otherwise acting as an agent of Satan, tempts Eve to eat from the tree of knowledge of good and evil. Eve eats, Adam eats, and they realize that they are naked. God sees their shame, interprets this as proof that they have eaten from the tree, and, upon their confession, expels them from the garden, in some accounts for fear that they will eat of the tree of eternal life and thereby become like God.
In the Islamic version of the story, the ideas are further expanded--mankind alone is given freedom as the caretaker of God's creation (prior to the fall, of course), and all creatures bow down before him at God's command. Satan and the fallen angels refuse to bow down, however, and therefore become the forces of temptation.
The pertinent theme we see in this story is one of conflicting freedoms. As the scene opens, we see that God has exercised a unique freedom: the freedom to create, ex nihilo, both in form and in law. But, later in the story, mankind exercises a freedom that not even God has: the freedom to transgress. God, by virtue of the very fact of his omnipotence, cannot transgress his own laws; any transgression by God's part is de facto not a transgression, but a suspension of the law.
This conflicting freedom, the freedom to transgress the law, is what must necessarily exist to put man in any relationship to God. Mankind stands in contrast to two other groups--the animals and bulk of creation, who are in complete compliance with God's law, and the fallen angels, who are in complete refusal of God's law. Neither of these groups can have any meaningful relationship with God.
For the animals, their complete obedience to God's law makes them little more than cogs in a machine. This is not to say that God is uncaring or indifferent toward them, but rather to say that their obedience is meaningless to God. Lacking both the freedom to transgress the laws and the judgement to derive the laws (i.e. the knowledge of good and evil), there can be no meaning to their relationship.
The fallen angels, on the contrary, lack relationship to God by virtue of their total refusal to acknowledge the rule of God. By refusing God's rules and refusing to in any way enter into a covenant with him, the fallen angels have stripped themselves of all positive relationship with God. Their only defining characteristic, indeed, is their negative relationship--that which God commands, the fallen oppose. This relationship, though seemingly more willful than that of the animals, is at the end just as meaningless. It is important too, to note that if man did not exist for the fallen to tempt, there would be no purpose for them. They are relevant only insofar as they relate to mankind and, to borrow from the Islamic tradition, would by definition not have fallen had mankind not stepped in.
So now we are left with mankind, mankind alone who has both the freedom to transgress God's law and the knowledge that he is doing it. That places mankind in a relationship that is best embodied in the Book of Job, where Job knows well enough that he deserves none of the torments inflicted upon him, and has the choice to curse God and die. Both of these elements--knowledge and freedom--are essential to what comes next: Job's challenge to God. Now God's final answer--that his ways are unfathomable, that humans are specks of dust compared to God--is largely irrelevant in this analysis. What is important is that mankind alone, as personified through Job and his unique freedom, has the ability to live in relationship to God, a relationship so strong that mankind alone can question God, hold him responsible, call him into account.
And where does that leave us? It leaves us, in many ways, back at the beginning, where we have always already begun: with the question I intentionally left in suspension, because it embodies our calling God into account--the question of God's "morality." But it is my conviction that this examination is not meaningless or absurd in any way. We have hopefully begun an answer, or at least a journey toward an answer, to that evil that is within our own control, i.e. the freedom to transgress. This journey makes us ready to offer up to God our own response to the question that he must raise in our relationship of our own freedom. Just as we do not know what it is to create, to make the laws, and must thus ask God for an answer as Job did, God by definition does not know what it is to transgress. We must take the meaning of "evil" not as an answer, but as a question--and in doing so, we must know that our freedom to do evil, to transgress, is the only thing that makes God accountable in our relationship for the other kind of "evil" that we question.