Well, I'm just asking one simple question right now. I believe what God says, too, but find that He speaks in different ways. For example, Jesus plainly said we need to eat His flesh to have eternal life (John 6:54), and those around Him seemed to take that literally. Yet we don't. Why choose to not take that literally, and then do choose to take Genesis 1 literally? I'm honestly wondering what reasons people have for making that choice.
First of all, taking Jesus in John 6 to mean his natural flesh and blood is not taking Him literally, it is taking Him to be speaking of natural things. One can take Jesus literally there and believe He is speaking of spiritual things. Literal does not equal natural, it means taking the bible in context at its word. Jesus taught things that we are intended to take literally, but they are things that are meant spiritually and not naturally.
Why should we take Genesis literally? Well, because Jesus did so. Jesus believed the first man and woman God created were Adam and Eve. Jesus believed God created the institution of marriage. In other words, Jesus believed in Genesis chapter 2 exactly as it is written. Jesus believed in the flood in the days of Noah. He believed that all the wicked men of the earth were destroyed by water. In other words, He believed in Genesis 6-9 just as it is written. Jesus believed that God overthrew Sodom in the days of Lot. Jesus believed there was a man named Lot, that he lived in Sodom, and that God saved from that city before destroying it. In other words, Jesus believed in Genesis 12, 13, 18, and 19 just as it is written. Jesus took the bible at its word, and so should we. If the bible gives us a chronology from Adam to Abraham that is exact, we should believe it. If the bible says God created the earth in 6 days and rested on the 7th, we should believe it. If the bible says God created the world out of nothing, we should believe it.