In order to be Omnipotent, or all knowing, as well as Omnipresent and all powerful wouldn't a supreme being have to be so far removed from concepts of "Good" and "Evil"? Those are just terms and ideas that Man created, therefore how can something that is literally the sum total of everything be one or the other?
If you're asking for an answer from a Christian perspective, which implies that you will accept, for the purposes of the answer, the presuppositions inherent in a "Christian answer" such as that God is who the Bible claims he is...
You're making a false assumption in the question. Good or evil are not concepts that man made up and applied to God. Good and evil are concepts defined by God, and understood by us, his creation. As the Creator of the universe, it is He who defines what anything is. He created things as he saw fit, and if He says something is this, or something is that, it is so.
We, as His creations merely understand, through the senses and ability to reason that he created in us, or through his revealed word to us.
Therefore God defines what good and evil is. Being God, it makes sense that "Good" is defined as according to His word,in line with His character, and as revealed to us by Him.
It is only from an atheistic mindset that one could claim that "good and evil are traits we made up and applied to God". The ability to say that cannot exist without the presupposition that God is imaginary, and a creation of man. From the Christan perspective, this is exactly the opposite of the truth.
Part of the problem (for me, at least) is thinking of good vs. evil as a kind of left-right spectrum. I don't know if that makes sense but it does seem to lead to some common questions like "how could a good God create evil?" Over time my mental model has changed so now I see God more like the center of a circle and all the rest of us are scattered somewhere between that center and the edge. God, the center, is the Way, the Logos, the Natural law, the divine Order. The further away from the center you are, the "less good" you find yourself, or the more disordered or out of harmony with God's will.
Allowing for mixed metaphors, this is similar to how Lao Tsu described the Tao, or how Buddhists might describe Karma. You are either in accord with Tao or you are not. You either have Karma or you don't (the pop notion that there is "good" karma or "bad" karma is incorrect). Conforming yourself to God's will, or discovering the Tao, or ridding yourself of karma... all of these involve ridding yourself of earthly desires and moving towards the center of that circle, God, which is true goodness.
From a Christian perspective, you have the question backwards. You're asking how we can say God is good, but we aren't the originators of that definition. God has defined goodness (and he has defined himself as good) and our definition is only a pathetic approximation of that concept. (This reminds me a bit of when Christ asked, "Why do you call me good when only God is good?")
Now, does God measure up to our petty, and woefully inadequate standards? I would understand if someone were to argue "not really," but the failure is in that we, as sinners, have a corrupt view of "good" (planks in our eyes) which is often deficient and self-contradictory. Should God be required to meet such a standard? Absolutely not.
Based on a comment above, I feel that it is only appropriate to state this:
Arguing that "good" and "evil" are relative, at least to a Christian, is an equivocation. Even if "good" is taken in a philosophical or ethical sense (as opposed to an adjective one might use to refer to one's coffee or "a merchant's goods"), that is not the same understanding of the word that comes from a theological sense. In philosophy, often the highest "good" of man is no more than himself (some might say it is "happiness", others might argue that it is "the betterment of society" however in both cases the end of "good" is man (and whether that is corporate or individual man hardly matters)), but the Christian views the highest good as something wholly external. Ours is an objective good which is good, whether we like it or not, and whether or not it seems like it profits us as individuals or a society.
These two approaches are vastly different and yield strikingly different results. In the ethicist's world men are larger than anything else, but they are only capable of reaching so far. "Though I stand on the shoulders of giants, I still cannot reach the stars." In the Christian world, men are microscopic but they stand on the shoulders of the almighty. "Though I am too small to see through the crowd, I will climb a sycamore and dine this night with God." In the atheist world, the greatest men strive to be übermensch, in the Christian's world we are already the likeness and image of God, and God himself has sacrificed himself for our redemption. We do not strive to be greater than men, we strive to be like God Himself.
Nothing exists that does not follow any rule. Everything that exists follows some rule or the other.
In any set or group. if the members do not follow their rules, they will be dumped, or thrown out of that group and will be considered "evil" by that group. Materials that are not fit to become part of our body are excreted by it, and will be considered "EVIL" or unclean. We will keep a distance or isolate them away from us, or keep it "out of sight".
In Christian belief, out of the set or group of all things created by God, creatures or material that stop following God's laws become unfit to be part of God's Kingdom will be kept out of it. They will eventually be destroyed.
Sometimes evil or dis-order is deliberately kept alive to teach new members. Where they teach to assemble or repair cars, cars are deliberately dis-assembled, and broken or worn out parts are saved (not thrown away) to teach new mechanics how to distinguish unfit parts, and how such parts can prevent the smooth operation of the engine.
If you say that God is "removed from concepts of 'Good" and "Evil'", then you are also saying that God is removed from any concept of a hungry child in pain. Which makes God less, not more. In other words, God IS capable of understanding suffering.
And as soon as we acknowledge that there is indeed suffering in the world, then there also most be evil.
Why - because it puts all of us in a position of either choosing to live in such a way as to increase suffering in the world (evil), OR living in such a way as to reduce it (good).
im proud as a being that you have asked such an obvious yet considered complicated question.
and heres my influence (power), good and evil or the moral perspective, is a human perspective. and not a gods perspective. which humans just tell each other that this is so when there only seeing it from one side of the coin if you like, infact for a god to say otherwise would merely be looking at it from the otherside, but god doesnt say this.. we do. we interpret thus from the live (spelling of evil backwards hmmmm?). god is neither heads nor tails to me.. he is heads, tails, and the coin itself which is both physical and non phsyical which is considered to be singular but when you put it under a microscope has many different parts to it, the alpha and omega, the unmoving, mover.
therefore god is neither good nor evil because hes neither physical or meta physical he is both.
good and evil is just a human perspective on concepts like up and down, left and right, small and big. in order to understand small there must be a big and one must have experienced what big is first before using the reference small. im not calling your answer or even question right, because right gives the prospect that what others are saying is wrong?? it just a case of what you believe serves you.
for me it doesnt work to say that the 'supreme/all' being is a vengeful and jealous being, if our aim through religion is to understand our connection to one another and bring divine joy. its not a case of what we think or believe god to be, its more a case of what we think and believe ourselves to be. thanks for your time :)