Perfection?

If god is perfect, why does he make so many mistakes? Let's take the story of Noah's ark, for instance. In Genesis 6:6, god is repentant for creating man. This is an explicit admission of a mistake on god's part. He feels sorry for what he has done. So, he decides to wipe the Earth of all creatures to wipe out the wickedness of humanity, thus taking out his anger at humans on all animals.

According to Xians, we are all wicked, so why is there still wickedness? Didn't god wipe it all out with the flood? Shouldn't he have known that his plan wouldn't work? In Genesis 8:21, he again seems to be repentant for doing what he has done, which is another admission of error as well as an admission of immorality. Why worship this god that obviously is incompetent and immoral?

Noah

I said I'd get to this sometime. When Noah was SIX HUNDRED YEARS OLD God told him that, although the rest of civilization were full of sin, Noah was perfect; thus, Noah was instructed to build a 450-foot boat. With eight people.

When the Ark was ready, two of each species were loaded on. (Where he got penguins in Israel I don't know. Presumably he took the smallpox virus with him as well.) Then God made it rain for forty days and forty nights. Which would make quite a puddle. Whether the entire Earth would be swallowed up by that is doubtful. Where Noah got water for all the animals I don't know either.

My point is that the Bible shows large marks of human creation. Although hardly anyone believes this story, my question is why anyone believes the other ones.