Those before Christ

In the first part of The Inferno, Dante finds out what happened to those who died before Christ came. All except those majorly used my God were sent to Limbo for eternity. I really don't understand this. They, of course, didn't have the choice of becoming a christian and following the teachings of Christ because he hadn't yet come. The people before Christ were told to make sacrifices of clean animals to God as a sacrifice for thier sins. If they did that, then why were they not allowed into heaven. Why were only certian people who did major deeds for God get into heaven such as Moses, Abraham, and Noah? What about the shephard who lived out in the country with his wife and kids who always followed Gods laws... prayed and provided for his family, loved God with all his heart, and kept the sabbath holy? Was he punished for the rest of eternity in Limbo just because he was one of the unlucky ones who wasn't an Isaelite or used in a miraculous was by God or born during or after the time of Christ? Who God really do that to a devoted follower? I don't see God doing that to someone who followed his laws, and sacrificed clean animals for their sins. Being a loving and just God as he is, I don't think be would ever let one of his followers end up in Limbo for eternity.