Making Superman an "alien" runs counter to his whole myth.
I don't think there will ever be a well-received Superman reboot ever again, or at least until the world goes through a massive cultural shift.
Unlike other superheroes, Superman is a cure-all. When all else fails, call Superman. He's a one-button solution to crime, mayhem and cataclysm. There's no reason for him to have detractors: he's not a vigilante, and his abnormality was never regarded with negative social terms like "alien" or "mutant". He's an adopted son of the mythical United States of America™. Crowds in Superman movies are never ambivalent: they are scared, they need his help, and they are grateful when he shows up.
In short, his whole myth lacks dramatic conflict, and audiences are too sophisticated now. They want their heroes to have internal demons, or to be outsiders, mutants, or in disguise.
Superman II was the last great use of the character. But you can't do that story over and over again, where he renounces his powers and allegiances. And no matter how much the comic & movie pimps try, you can't keep rewriting the origins and motivations of superheroes to suit your marketing research. Changing who Superman is turns him into someone else.
It's interesting that 2 different reboots in the post-9/11 world have failed, because that kind of world is the one that gave birth to the myth: the rise of Hitler and WW2. People needed a one-button solution to the scary evils of that uncertain time. But while there was a brief "death of irony" period after 9/11, it didn't really last that long. And making an outcast Superman is just doing Superman wrong.
