When Paul wrote 1 Corinthians 15, he did so under the assumption of a theistic, specifically Jewish worldview, hence why the rest of verse 17 says "ye are yet in your sins". Paul never intended, at least directly, to apply this concept equally to atheism. Nevertheless, I contend that it does. If there is no God, that still means Christ isn't raised, and so our faith is still in vain. But in the case of atheism, it is all in vain, right down to the Ten Commandments.
The science fiction show "Primeval" is a series about rifts in time that allow anything that walks through them to travel to either the past or the future. Naturally, the show assumes Evolution to be true, meaning there is no God, life is an accident, and human beings are merely hyper intelligent apes that appeared millions of years after most of the other creatures in the show. As a young boy, Patrick Quinn gets lost in one of these rifts and spends years travelling through time. In season 4, he finally finds his way home.
But what he has seen has diminished his view of morality and meaning. He begins to question the existence of morality, asking the question "why are humans different"? And indeed, if we are not made in the image of God, why are we any different to the animals we put on our plate? Why are we any different from a lion who kills without mercy? Why is it evil when a man kills a man, but merely a tragedy when a rock does?
When we take God out of the picture, we devalue life and remove the need for morality to exist. Though Primeval presents Patrick as a bad guy, he has a serious, philosophically sound point that should make us seriously consider the value of faith to our universe. Christianity is the only faith that answers the question "why are humans different?" The answer: we are different because we are made in his image and called to his purpose. We have value because if we were to genuinely go back to the earliest stages of the earth, we would not find a world full of dinosaurs and devoid of humans. We would not find ape men sitting by a stream. We would find our ancestors, fully human, from Adam to Noah, from Noah to Jesus, from Jesus right until this very day. Humans are different not because Ethan would be wrong in his world, but because Darwinists are wrong in ours.