I sort of like the idea of just simply naming it Superman. It would be a good way to really start fresh.
Though I like some of the other suggestions, like Superman: Last Son of Krypton, I think that's a mouthful.
Perhaps it could go something like:
Man of Steel
Man of Tomorrow (though I guess it would probably be redundant to use man twice)
Last Son of Krypton
Superman has universal name recognition. I don't think his name has to be at the beginning of each title so long as its announced in the commercials and his "S" shield is prevalent in the marketing of the film.