1. As big a scale in action and threat as the first one
2. Alien villain (Brainiac? Doomsday? Darkseid?)
3. IF Lex is in it, as a background/supporting adversary NOT the primary villain. Just stirring up the public against Superman.
4. Superman does more to save innocent lives in the middle of a fight
5. Superman gets to show a sense of humor
6. Show more of Superman co-operating with the military/police
7. subtle lead-in to Justice League