My brother and I often have conversations about God's existence. He is definate a skeptic who believes that the rest of us have created a being to satisfy our need for answers. Certainly, when someone has such an anti perspective there is no logical agrument that is going to change their mind. So I have asked him to try an experiment (whether this will work or not I do not know, but I know that if we take one step toward God, He'll take at least two toward you - so I am hopeful): I have asked him to talk to God everyday for 40 days. He needs to tell him his concerns, his faults, his questions. I believe as this conversations unfolds, he will see that it moves from a one sided to a two sided conversations.
It will be interesting to see if the skeptic is willing to give it a try. I encourage you to pose the same challenge to other non-believers. I would live it if they would comment and let us know how the experiment unfolds.