I saw this article on CBM http://**************.com/fansites/CaveOfSolitude/news/?a=35472
and i find it to be an interesting theory on how kryptonians could be introduced to the story.I thought it was a Great approach.Heres a snippet from it.
With that said, how better to tie the character of Superman to our present than by relating our unexplained history on Earth to the history of Krypton? What if a group of ancient Kryptonians found a way to come to Earth and act as Gods among mortals (see egyptian God of Sun Ra for example or the various Gods based upon the Sun which would power these Kryptonian deities)? This scenario could easily be weaved into a story about how the prideful majority of Krypton frowned against this practice of ruling over a primitive Earth and eventually punished these Kryptonians who pretended to be Gods for sharing tidbits of technology and culture with the likes of earthlings. That could be an explanation to why all of a sudden these Gods disappeared from Earth leaving nothing of their presence other than colorful hieroglyphics and amazing temples (example Egyptian and Mayan ruins).
This could also tie into a Birthright story line where Clark is travelling the globe, almost like an Indiana Jones of sorts unlocking his Kryptonian past through remnants left behind around the world reporting as a travelling journalist on these wondrous sites. This could also explain why Kal-els parents knew to send him to Earth and why Zod eventually shows up, knowing that he could rule as a God following in the footsteps of those earlier Kryptonians before him (which he could be a descendant of perhaps?) What if Clark was content with not being a public figure until Zod shows himself first, claiming to be a returning deity who will rule the world picking up where the ancient Gods left off. At first they are unaware of eachother, but Zod could fill Kal-el in on his heritage as he tries to convince him to rule along side of him. Clark could then realize Zods true intentions to be Earth's dictator. This could be the motivation for Clark to rise up and take up the mantle of Superman.