The man who invented/discovered the Christian notion of God was Aristotle. The theory of the Unmoved Mover. He makes a rather complex argument for this theory and that argument is called the cosmological argument. This is the logical foundation Christianity still is dependent on. The universe has to have a beginning. According to Christianity, this by necessity, has to be God.

http://en.wikipedia.org/wiki/Aristotelian_view_of_God

Aristotle reasoned that since God was the initiator of all movement and actions he was also the originator of thought.

God is omnipotent and had everything he wanted. This is supported by a rather complex argument. This argumentation is also critical for the Christian theory of God. But here is where Aristotle differs a bit from modern Christian thought. He reasoned that all our emotions are based on things we lack. God doesn't lack anything therefore has no emotions. God is pure thought. His theory is a lot more complex than this. This was just a short run down of it. I didn't find the complete argumentation, but I'm sure I can dig it up if given enough time.

Philo of Alexandria shoehorned this theory into Judaism, and hey presto we've got Christianity. We actually also got Judaism as we know it today. It wasn't monotheist before this.

Anyway... This was a long winded way of saying that there are plenty of philosophical arguments for God being neither good nor evil, and this is the roots of Christianity. By claiming God is good you're standing up in the boat inserting all kinds of logical inconsistencies. It's a very complex theory and best not tampered with if you want coherence.

How do you know whether the goodness of God is just not wishful thinking from your side? Are there any logical arguments supporting God being good? Anyway... this is very complicated. Every act has a consequence and by being good to somebody God is bound to be evil to somebody somewhere.

The theory that God is good is not an easy theory to support. I don't know any philosopher who has managed. Thomas Aquinas just made the statement that God is good, because God is perfect and goodness is intrinsic with perfection. I personally can't see how that follows logically. I'd love to be enlightened.