From a biblical perspective......
It is written that the things of God are apparent in what was made.
That it is good to love your neighbor is obvious -and it is also written that because such things are obvious, those who do not are without excuse.
Yet another verse essentially says that if any keep the law of love -regardless of belief -it is still counted as righteousness, and they will fare better in the judgment than those who believe but do not keep the law.
If you honestly, sincerely and innocently do not believe, you cannot be expected to.
That is not the sort of "unbelief" spoken against in scripture which will be met with a harsh judgment later.
At the judgment of all who have ever lived, "the rest of the dead" who were not called to the first resurrection (God did not even plan to call all to the first resurrection -and none can come to God except that he calls them, anyway) all will be "judged according to their works" -not their previous beliefs. That is only fair, as some will never even have heard of Christ or the Father, etc.
At that point, the existence of God and Christ will be rather apparent -so Atheism won't really be an option.