Hello--new poster here and I read through this entire thread but did not see a great Christian response to the original post and lots of atheist responses.
My background is from the Eastern Orthodox Churches, I am just a lay person and do not consider myself an expert on theology or doctrine, but have read a good bit of the writers (modern and historical) of our Church.
I think it could be useful to break down each of the assertions the original post makes:
1. Earth was created in 6 days -- Not all Christians believe this. The Orthodox churches for example would largely say there are differing interpretations of what the day timeline in Genesis means, and disagreements of it would likely not rise to the level that it would cause churches to stop being in communion with one another.
2. Earth was created 6000 years ago -- Not all Christians believe this. The Orthodox churches, like with the 6 day timeline, would not take any strong stance on this issue. Some Orthodox believers are aware of the timeline that Archbishop Ussher created which is the primary basis for the 6000 year argument. There is nothing in this analysis which is core to the faith, and disagreements about it would not cause one church to view the other as schismatic, at least among the Orthodox Churches. While I know less about the other Christian groups, my understanding is this is a similar view to the Roman church and at least some of the Protestant churches.
3. Dinosaurs ruling the earth for millions of years with no comment from religious people at all -- This is not true, there have been Orthodox Bishops and Priests who have spoken about dinosaurs and other prehistoric life. They do not find any reason to doubt dinosaurs existed on earth, millions of years ago, and that they long predated humans.
All I have done here is say "hey, not all Christians believe these three things", I will try to go a little more in depth so please bear with me.
The view that Genesis is a literal history of events, and further that we know exactly when and what those events were, in sequence, is a view that treats Genesis as a historical record. My view, and the view of many Orthodox Christians and probably many other Christians, is that Genesis was not made part of inerrant scripture for the purpose of telling a history of events. Even without any science at all, it is easy to arrive at a conclusion that Genesis was not intended as a historical record. Our view is it was intended as a source of theological truth, and the important theological truths are the understanding that all of creation was created by God, that humans were created by God, and other important theological truths of Genesis. The age of the earth, the number of 24 hour earth days in the creation sequence, the history of the animals and such is not core Christian theology, and thus one can interpret them freely without being schismatic or heretical. It is just fine if you want to believe it was 6000 years ago and through some unknowable divine mystery, all evidence shows it was much longer, but it is also valid (and my belief) that creation was many billions of our years ago and earth and its life was formed over billions of years.
The more advanced our science becomes, the stronger it makes my faith in God and it aligns very tightly with Orthodox doctrine. Orthodox believe we are on a path to theosis, or oneness and likeness to God. It is my belief that many things in the bible are presented in a way for us to understand, because 2000 years ago we could only comprehend in certain ways. Even now we can only comprehend a little better. Galileo had this same view--learning about God's creation through science actually can bring us closer to God. God's divine nature is not knowable to us living humans, but we do believe that we are all on a journey towards knowing it, and that this journey continues in death.