I'm not writing this to demand that you become Christian, or to suggest somehow that non-Christians are terrible people. My intent is two-fold. First, to get ideas out of my head and reform them more objectively on paper. Second, to perhaps demonstrate why thinking about what happens after we die is important.
I am intentionally not citing any particular sources. You'll have to do the research on your own - it is worth the trouble.
There is clearly right and wrong in the world. We may disagree on precisely what is right or wrong in every day matters, but we recognize that there is some standard. But where does this standard come from?
It is clear historically that Jesus existed, and what he has said and done is well documented. What we disagree over is the significance. If the things that happened are true, and what is said can be trusted, then submitting to Christ is clear. It is much more difficut to explain why some part of this is false, and maintaining consistency in the history and consequences of this.
The notion that there has always been a God explains (in a general way) how a universe could be formed. This does not invalidate ongoing scientific research. It just provides a context for all the things we can study or observe.
I suspect that many people are turned off from Christianity (or religion altogether) because of the hypocrisy that exists. How can Christans teach us to love one another and continue to lie, steal, murder, or flip people off in traffic? The truth is that we are sinful by nature. Accepting Jesus as penance does not in itself change our behavior (but we do get the benefit of the Holy Spirit). We are instructed to invest in a relationship with God through study, prayer, and community to fight against our evil tendencies.
One of the other great criticisms is something to the effect of "How can God allow people to suffer/{synonyms} if he is good?". I think people have been given the choice to follow God, or follow themselves. It is only through the ability to choose that God can have relationship with disciples. Otherwise, everyone would be forced to obedience, which isn't anything special.
If nothing else, Christianity gives us purpose and a chance at living forever, in peace.