The entire idea of salvation in Christianity is a bit troublesome.
The idea that the only way to salvation lies through Jesus is the central idea of Christianity. In fact, it is really the only one that matters, as Christians will tell you all of their faith is built on that simple notion.
But this idea is built on a few assumptions about the world:
1) Man is inherently born sinful (because of the original sin of Adam and Eve).
2) Sin is a bad thing and we should strive to avoid all forms of it.
The first may be a nice metaphor, but it is ridiculous if you examine it factually.
For one, it is a known fact that there never was any "Adam and Eve". Despite the popular denial of such, the evolution of species, including humans, is an established fact. There never was a breeding population of only two humans because for one, such a population cannot sustain a species due to a lack of genetic diversity, and if such a pair existed our gene pool would show evidence of it today.
The reason why we can know this lies inside the human cell. In each of your cells there are tiny "organelles" called mitochondria. They're basically tiny energy factories for the cell. They convert glucose (blood sugar) and oxygen into ATP, which is used to store energy throughout the cell. But each mitochondria carries its own DNA, completely separate from your normal genome. Unlike your normal genome, half of which comes from your father and half of which comes from your mother, your mitochondria come entirely from your mother alone.
Hence, barring mutations, your mitochondria are the same as your mothers, but not necessarily your fathers. If there were a single mother to all people today, such as Eve, we would see the evidence in mitochondrial DNA. Every person's would be a slight variation of the same overall plan (the variation due to mutations that built up over 6,000 years). Of course, all people were wiped out at some point, but only one line would have been kept alive through Noah's family. But instead we don't see that. By inspecting different people's mitocondrial DNA, geneticists can actually estimate based on their diversity how separated groups of people are, as well as how small their breeding population was in the past. And it shows no evidence of a single mother at any point in history.
So, what can we conclude? Adam and Eve never actually existed. That means that the original sin described in Genesis never even happened. So now (unless you interpret the whole thing as a metaphor) we have to determine that the entire point of salvation is lacking. What's there to be saved from if there is no original sin? The entire argument that you can't just be a good person, you have to be good and you have to accept Jesus, falls on its face.
Going back to our list of assumptions, let's look at number 2. Is it really true that all sin is bad and should be avoided? Obviously things like murder and theft are bad, but what about "Honoring thy father and mother"? Surely its a good virtue, but how many children grow up in abusive homes? Should they be condemned to hell because they resist abuse? And what about "remembering the sabbath and keeping it holy"? Does that mean that working on the sabbath or missing church should be rewarded by an eternity of pain and suffering? Patterns I notice when talking with Christians is that they love to go on and on about how good their moral code is, by bringing up obvious taboos such as murder and theft. But they never want to talk about the Bible's many rules against such things as wearing mixed fabrics, eating non-kosher, and working on the sabbath.
Not to mention the fact that whenever you bring up the Bible's orders to execute sons who disobey their parents, people who work on the Sabbath, and girls who marry despite not being virgins, you are instantly dismissed as a rude atheist. Can you imagine what their reaction would be if someone like O'Hair ever wrote such a pack of abject brutality as ethical guidelines for the atheist? How willing, do you think, would the Christian be to accept the feeble excuse that Richard Dawkins later "undid" her commandments in his new book? The Christian mind, while sometimes grounded in goodwill, is ultimately, ironically, the most hypocritical in imagination. With one breath they extoll the virtues of their prophet's teachings, and in the next they loudly inform everyone of how much they pray for those who disagree (Matthew 6:5-6).
The reason why an atheist is so obsessed with Christianity is not because they are bitter, or because they secretly believe in god. It is because the Christian faith is such an intriguing mess of contradictions and hypocrisy. There is no more ironic statement than a Christian telling an atheist to be open-minded. Here we have a person who takes the fact that their faith has no basis in evidence as a good sign, a person who when they feel doubtful, reassure themselves that doubting their faith is a sign that it is more likely to be correct, a person who views anyone outside their faith to be at best hopelessly misguided and at worst to be little more than an animal. And this person is telling someone who is aware enough to apply the same skepticism the Christian applies to every other faith in the human imagination to their faith to be "more open-minded".
It is no coincidence that Christians do not preach to their followers to be more open-minded about Muhammed, and tell them to keep in mind that the Muslim faith might be correct. It is because a Christian really doesn't understand the concept of being open-minded. To be open-minded is to be free of all prejudices both against something and FOR something. Because giving special credence to the Christian faith is the same as being closed-minded towards some other faith. Christians want all the privilege of being the strong and correct majority, while retaining the moral high ground of being a persecuted minority.