Why didn't God just start again?

Some people claim that God was planning to start again at various points in the Old Testament, but that something persuaded him not to do the job properly.  The flood was a fiasco and the whole story of Sodom and Gomorra would frankly not have achieved enough.

But all of that was much too late wasn't it?  He had let things go too far.  And yet, omniscient and omni-benevolent God had seen what had happened in the Garden to Eden when there were only two people there.  Obviously he new what was going to happen as history progressed, and that he would end up 'having to' send billions of people to hell for eternal torment.  (Why he still had to do this just because to the irresistable power of 'original sin' anyway is a separate mystery.)

Yet all of that suffering could have been easily avoided if he had just wiped out his (presumably) first attempt, including Adam and Eve and had another try where he didn't put that powerful tree within reach of his favorite creatures.  Surely that course of action would have been for the greater good.

It's not as if it had taken him billions of years to do the whole creation job after all.  Another six days of work and he could have rested again, secure in knowledge that fairness had been well served.

But no - instead of that much of the population of the world lives in dread of hell. 

Surely that is evidence enough or substantial underachievement!

Small note:  Yes I know that not all Christians believe in the literal truth of Genesis!