Probably a movie from the 70´s . Holocaust happening, everyone dissappered from the face of the earth except a man and a woman, N York probably. Then another guy is found and both man start fighting over power. They want to rule and I think they want also the woman. I can´t recall if one of the actors is Sidney Poitier . Can you please help on this one?? Thank you so much!!

Sounds like The World, the Flesh and the Devil (http://www.imdb.com/title/tt0053454/)