This whole "God is perfect" thing is rubbish and I will attempt to explain why. Perfection is subjective. For example, the perfect evening differs from person to person. One might include dancing, while another may require liquor. This is true for everything. Thus, why there is nothing in existence can be agreed by everyone to be perfect.
Now, how this applies to a deity if twofold. One person saying God (judeo-christian) is perfect, is false because not everyone may see it that way. So, even if you happen to think God is perfect, the truth is much different because that is only your subjective opinion and opinions don't make facts.
The other half is the assertion that God is inherently perfect; a quality of being God. This is labeling God with a subjective adjective, it's like saying God is funny (or more correctly, the funniest). By whose standards is God the funniest or perfect? If God does exist as a supremely powerful being who exists outside, but not constrained by, the laws of the physical world including time and space, as a fickle arbiter who plays favorites and kills wantonly with the callous and random touch as it's portrayed and preached, then surely we aren't able to label perfection; being burdened by the laws of physics and hampered by humane feelings.
As a fact, God cannot be stated as perfect, nor can it be a quality inherent in itself as seen by us.