For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Kenneth Heck
The answer to this question hasn't been specifically revealed by God. If we truly knew the answer today we might be contaminating humanity with premature knowledge which could demoralise everybody. We can only speculate, mostly from human experience, about possible answers.
Why do human beings create? Mainly because we want a better life than
we would have otherwise, and there is also the commandment to multiply and be fruitful. (Gen.1:29). Even though God is perfect according to our scriptures and human understanding, it doesn't mean that He may not want to progress in perfection in a way we are unable as humans to understand, since he is already beyond our understanding.
So, one answer is that before God created the universe He was preparing to create the universe in order that, through this act, He will become more quintessentially God than otherwise. In fact, our current universe may not be the only one He has created - there could have been others beforehand which also served the same or similar purposes.
Nicola H
Somewhat egocentric to think that without us God's existence was lacking in any way. Who are we but mere mortals. :-)
Ni Jay
Here is another question of a divine nature which we are attempting to answer using human logic. It is an impossible task because our minds can't even understand the complexity and logic of much of the creation e.g. the big bang, the invisible soul that drives us, why some are born with illnesses, deformities, ailments and in to poverty from birth while others are not, why natural disasters happen for some but not for others. So what chance have we of guessing what the creator was doing at any time never mind before. All what we can do is speculate using human notions as measurement, evaluation and assessment instruments. God is everlasting, omnipresent and eternal which means that there is no 'before' and 'after' states.
Reinhard Illig
The evidences from scripture are brief at best but that is all we have to go on. For us to answer concerning God using our finite minds can probably be best understood as an ant describing Creation and Redemption.