If there is a God, which the majority of people who have lived believe that there is and if there is sin that every person commits which we all know is true and if God is perfect and has never sinned which would have to be true for us to have a standard of goodness we could depend on and if our sin made it impossible for us to have fellowship with a perfect God then basically every day we're alienating ourselves more and more from this God and are (as C.S. Lewis so rightly puts it) no likely to do any better tomorrow.
If that is all true and our purpose here on earth wasn't to make money or to create a wonderful life for ourselves but to discover this truth because this life isn't all there is - if in fact we are all going to live forever but where you live is determined by whether you are reconciled to God or not then suddenly things get very interesting.
We must find a way to be reconciled to a perfect God so Muslims and Hindus and Buddhists and even Catholics say we should do a lot of good stuff to a bunch of people and this will lead to a happy ending when we die but Christians say something else entirely. They say that you can't possibly be perfect. You can't stop sinning even if you want to stop sinning. It's impossible. The only way we could be reconciled to a perfect God is if the God we have wronged by sinning made a way for us himself and this is what we find has happened.
God had a son who took the form of a man, lived a sinless life while on earth and became a perfect sacrifice to bear all our sins when He was put to death. The bible called him Jesus and non- biblical sources confirmed his life and death and thousands of eye witnesses confirmed his resurrection. This Jesus offers us forgiveness for every sin we've ever committed or ever will commit if we will accept it but only if we accept it.
We can do it our own way and try to be nice or give a bunch to charities but if the God we've offended says that that won't cut it then it's utter foolishness to keep trying a way that will never work. In the end if we truly want to know why we are here and what it's going to take to spend eternity reconciled to God in a place called heaven rather than separated from God in a place called hell then we must get the rules from the one that set them in place. That's the gospel and it's what God and Jesus have told those that have accepted this forgiveness to proclaim.
Do the research, question, examine everything that's out there, think. Don't just live blindly believing you have no purpose and that you return to dust when you die or worse still you get to come back to try harder in another life. Christianity doesn't have all the answers but it is not self contradictory and it has stood the test of time.