Why did God wait so long to send Jesus? Weren't there tons of people prior to Jesus? It seems like God waited too long especially since human beings have been around for 100 million years.

What is really crucial here is not the amount of time that has elapsed but the size of the human population.  The population reference bureau estaimtes that the number of people who have lived on this planet is about a 105 billion people.  Only 2 percent of those lived prior to the advent of Christ.  Erik Crapes (sp?) of the survey research center at the University of Michigan's institute for Social Research says, "God's timing couldn't have been more perfect, Christ showed up just before the exponential explosion in the worlds population.  The Bible says that in the fullness of time God sent forth His son, and when Christ came, the nation of Israel had been prepared, the Roman peace dominated the Mediterranean world, it was an ge of literacy and learning so that the stage was sent for the advent of God's son into the world (Taken from Craig's debate with Christopher Hitchens).