Both films show the physical and cultural effects a society can have a person. Just as the Bruce Wayne story could not exist with the massive skyscrapers and colorful citizens of Gotham, Jamal from "Slumdog" would not be succeeding on the show if it wasn't for the slums. However, beyond the physical is the cultural. Batman exists because he thrives off the fear of the criminals of the city. Jamal answers questions on the show based off cultural experience, a hodge podge of almost every cultural aspect of India, from cricket to celebrity figures to mantras on it's flag.
And finally, both films are very traditional stories at heart. Jamal is noble "knight" driven by never ending love for his princess. He undergoes many trials on his quest, including a climax with the King (the millionaire host (why is he the king, cause he's got the loot ). Batman is a knight driven to save his kingdom, at great personal cost to himself. However, where one film shows the toils of being a hero and believing in good, the other film soars on the power of hope.