Philosophically that is. Psychologically he fulfils an important role – to distance us from philosophy.
In no way would the existence of a God alter the important properties of the universe. Most of the problems a God supposedly solves are merely shifted to the other side of him – a step further away from humans, where we can comfortably ignore them.
Some solutions God doesn’t really provide (presumably all thought of before by various philosophers, but I don’t know which ones, and it’s irrelevant, so please excuse the plagiarism) :
Creator of the universe: An obvious one. Where did God come from then? If he’s existed forever then so could a universe. If you think something as complex as a universe couldn’t come from nothing, how complex would God have to be to be able to make universes?
Source of morality: Where does God get his moral principles from? If he invents them himself they are just as arbitrary a set of restrictions on behaviour as any other (such as an atheist’s morals are feared to be by the religious). Why follow them? If they are inherent in the universe, related to other people, or a matter of choice then God isn’t needed.
Morality is a set of value judgements. If God and I both have a set of value judgements (a moral code), to say that God’s takes precedence is a value judgement in itself. Who judges? God? Why?
Provider of free will: For reasons discussed in the previous post, Free will isn’t a concept (unless you mean determinism), God can’t have – or give humans – free will which isn’t deterministic. The absence of God’s ‘free will’ is even more apparent if he must be good all the time (unless he invents his own changeable moral code as he goes, but is that the kind of morality God should subscribe to? Well yes, if he does! But there’s still the old problem of free will not existing – he can’t escape).
If he’s all powerful as well, then he just ends up as another natural law – one that makes good things always happen. Anyone who’s been alive can tell you there’s fairly solid empirical evidence against such a law existing, but my point isn’t to draw attention to the problem of evil so much as to point out that natural laws are nothing new.
The final picture? A God who may well exist*. But who cares? Yeah, if he’s all powerful perhaps you should follow his moral laws just to stop him smiting you, but that’s politics, not metaphysics.
*except perhaps for the whole problem of evil bit – but goodness is hard to define, so let’s give him a break on that one for a moment