In a first movie, I'm hoping Superman is an alien... and gets all the human fears that go along with that: ie. humans should want to kill this potential invader, until his true motives are proven. That would be a most novel approach I think... with Superman appearing as an enemy to earth, until the climax of the movie, where Lex is revealled as the real baddy, and superman as the hero. Lois should be the 'everyman'. She should fear Supes at first, then, with Clark's help, become curious, to the point of discovering that this alien is actually a friend.
Movie should end with a spark between the two... saving romance for 2nd installment, with some tragedy at the end, set up a third movie.