It tackles arguments like yours at length, and is written by a former, and SERIOUS skeptic. Otherwise, just keep sitting outside that locked door, pretending you have the right to tell God what to do.
Which God?
The problem is that there isn't just one kind of non-Christian. There are many people who aren't Christian that could simply be classified as "differently religious", and these kinds are typically relatively easy to convert. However, there is a small percentage of the population that has no real religious tendencies at all, which is where Christians are doing a really bad job. The reason Christians are doing a bad job is that they assume that these people are merely "differently religious", which is hardly the case.
I would classify myself as one of those people that has never had religious tendencies towards anything. Nonetheless, I was raised in a positive and very religious environment and have been thoroughly exposed to just about everything the Christian religion has to offer. It just didn't stick, and lacking any obvious intrinsic value I drifted away from it. Explaining your religion to someone who essentially doesn't have the capacity for religion is like explaining color to a blind man. No amount of willingness to understand on the part of the blind man will make your explanations of color any clearer. Saying that the blindman is willfully ignoring the concept of color is nothing more than frustration on your part.
I think it is this second type of non-Christian (the ones who have no natural religious tendencies) that you and others are arguing with on these threads and you have to adjust your arguments accordingly. All intelligent arguments have to be made from premises that both sides agree on and developed logically from there. Assuming that both parties are honest (and I believe they are in this case), then you should be able to demonstrate the logic of your position without resorting to assumptions that aren't shared.