Well, a very good example of a doctrine that has been generally accepted for a very long time is the Doctrine of Endless Punishment. From what I've seen - most bible Christians agree that if you do not confess Jesus as your saviour before you die (and you've been exposed to the story of Christ), then you go to hell forever. Here is a link, if you would like to begin research on this yourself: http://www.tentmaker.org/books/OriginandHistory.html
Also, the Trinity doctrine. The word trinity isn't even in the bible. The Father, Son, and Holy Spirit or Ghost are - but the trinity concept of God being three equal persons - was invented by man. Also generally accepted by many of today's churches. You could also research this for yourself.
So yes, I have done research. There's nothing wrong with questioning the accepted. To be a Christian means to conform to the image of Christ - and as we all know from the story in the Gospel: Christ was definitely a free thinker. He was considered so radical that they killed him for blaspheme. Keep this in mind. "Those who have ears to hear" will understand his mysterious sayings, and truly hear what God is saying to them on a personal level. I believe in personal divine revelation of what scriptures mean - it's risky, because you could be wrong - but you pray for confirmation about it, and if it's true, you will recieve confirmation from God. This has happened to me many, many times. It's really quite an amazing way to learn about God.
But this is me. The other replier made a good point - it doesn't matter if no one seems to agree. We all are responsible for our own beliefs - no one else's. I was raised a bible Christian, and am simply hoping to help others think for themselves, as I learned to do. I suppose it is my own way of "spreading the good news". To me, the good news is: God loves the world so much that his grace extends far beyond belief systems and religions. That his love and grace comes in different forms - meaning ALL spiritual people can be saved - not just people who call themselves Christians. And that there is no such thing as eternal punishment. I truly, honestly believe - through years of personal divine revelation (prayer, contemplation, meditation, etc) - that people do not go to heaven simply because they do not feel worthy of God's love. They're ashamed of what they've done in life - of how they've been. If you die and you haven't forgiven YOURSELF for your sins - God will invite you, but you may decline out of shame. But He FOREVER will be inviting you - waiting patiently until you are ready to accept his love. This applies to all - even non-Christian suicides. I am sure of it. But definitely do not take my word for it - I have no obvious biblical proof of this, anyway. I am simply trying to share what I believe to be true - to come against the deception of the fallen angels, wanting people to fear death and the afterlife - keeping them in fear of eternal hell. What a lie - what a disgusting lie.