For as long as I live, I will never understand how anyone who has done more than casually glanced at the first 8 pages of a Bible could possibly interpret Genesis as anything other than historical narrative. Everything, from common sense to the rest of the Bible, prevents any alternative explanation.
First, there is the common sense element. No matter what language you read it in (especially the original Hebrew), there is no sensible way to interpret Genesis as anything other than historical narrative. In fact, when we interpret it as mere poetry, it becomes theologically meaningless. There is absolutely nothing you can learn from Genesis if it is made up. Actual poetry, such as the Psalms, convey deep spiritual truths. All you have to do is think, and even the most obviously metaphorical statement brings you the reality. But if Genesis is poetry, what does it tell us?
Aside from being the most obvious interpretation, it is also the oldest interpretation. I may not have scores of ancient rabbis to prove this, but thankfully, I don't need to, as there is an ancient Jewish work that was actually written around the same time as Genesis. And by the same author, at that. This book is called Exodus, and it so clearly states that God created the heavens, the earth, and all that is in them, in a mere 6 days. Moses was so confident in this that he actually based the doctrine of the Sabbath upon this. And of course, it wasn't Moses coming up with this stuff. Exodus 20:11, in which the command regarding the Sabbath was given, is one of the rare instances of scripture that was not merely inspired, but personally written by God Himself, upon two stone tablets. The historical Genesis interpretation is literally written in stone. By God. And I know I'm technically skipping ahead by giving Exodus as the example, but I simply cannot state this enough: Scripture interprets scripture, and is the final authority. Therefore, anywhere in the Bible that indicates Genesis is historical must be taken at face value.
And of course, for most of history, it was. To be sure, there are examples of people interpreting Genesis differently. None of them in the way OECs and Theistic Evolutionists do today, of course, but there were disputes about the interpretation of Genesis. Nevertheless, though these disputes did exist, the overwhelming majority of historical authors, from Josephus to Augustine to Calvin to Luther to Newton, show that the historical narrative understanding of Genesis has been fiercely dominant throughout history, even in the face of various pagan religions that preached an old earth. Evolution is the first religion to really make Christians want to change our views, mainly because ancient religions were openly religious, whereas Evolution is a pseudoscience on top of that.
The reason most Christians interpreted Genesis as historical narrative seems obvious. Just as Moses did, so also did other prominent Biblical figures, including Christ Himself. Peter even went so far as to link denial of the reality of Genesis with denial of the return of Christ (2 Peter 3:1-9). Ironically, verse 8 is often abused by Old Earthers to support the very denial predicted in that very chapter, illustrating the dangers of taking one verse out of context. I cannot stress this enough, read the Bible. Study the Bible. Even a stone cold atheist can read one verse without regard for context. As Christians, we need to be above this.
And so we see that the historical narrative interpretation really is indisputable. If you do dispute it, there is something very wrong, either with your spiritual life, or, at the risk of launching personal attacks, your mental capacity. Alternative interpretations of Genesis are better than alternative interpretations of the death, resurrection and deity of Christ in only one regard: Old Earthers will not necessarily go to Hell.
To me, this gives little comfort. Aside from the fact it is far better to live for Jesus, rather than just live through Him, our souls aren't the only ones in view here. It is selfish to spread such detestable heresies, because other people, who value consistency, cannot be saved just because you are willing to compromise. And as this is such an easy issue, if the Church does not stand on Genesis, unbelievers won't come to Christ. "You don't believe your own Bible, why should I?"
If you're an old earther, people mock Christ because of you. As it's not an essential issue, you may be saved yourself, but you are enabling Satan to flourish. If you lack faith, pray for more. If you're scared, pray for courage. If mockery offends you, swallow your pride, because they mock us either way. Whatever idols you have erected that prevent you from understanding the word of the Lord, destroy them. They are not worth you losing Heavenly treasures, or other people losing their souls.