I've learned more about religion (especially Christanity) as a new atheist over the last 6 months than at any time in my life.
1) The only accounts of a Jesus come 40-50 years after he died. And, the only accounts are from Christian historias. If you wanted a non-bias recording of Jesus from a Greek, or non-Roman historian you aren't going to find it. IMO, this is a big red flag on whether Jesus existed or not. I still think he existed, but I just don't think he was magical.
2) The gospels are filled with contradictions, and falsehoods. And, we don't have the originals. All that we have are copies of copies of copies of copiee ad nausem...
3) If God were omnipresent and all powerful, why are there cultures today that have no idea of the biblical god? My ex Thai girlfriend who is a Buddhist was like "who is this god? Jesus? She thought that he was a USA movie star. The bible has a ethnocentric view that was written with caucasian people in mind. Where are the native Americans? The Asians? The Pacific Islanders and Africans? Why would they be doomed to burn in hell forever, if they've never heard of the God in the bible.
4) Whose right, and whose wrong? Are the Muslims correct? What about the Hindus, Native Americans or Buddhist? Even within Christanity they can't even agree. I was born Catholic. I was told on multiple occasions that I was bound for hell by Baptist Christians because I prayed to a statue. And, that the pope was satan. Muslims think evewryone who doesn't bow to Allah is hell bound.
5) About Heaven and Hell. I picked up this wonderful book by Bart Erhman titled "Heaven and Hell. A HIstory of the Afterlife." Bart is a biblical historian who has spent 40 years of his life researching the old, new testament, the gospels, etc. He knows his stuff. He argues that Jesus never preached the Christian concept of heaven and hell. That the version we were taught isn't in the ancient hebrew text, and it's not found in the old testament. This makes sense since Jews believe in a very different afterlife than the Christian version which IMO was used to scare people into becoming Christians. If you want you can watch the video on YouTube.
Starts at the 12:25 mark
Dr. Ehrman on why the new testament is not reliable.