Seeing this tomorrow, so I don't know how good of bad it is but I'll just say this.
The only way this movie could be worse than Superman Returns is if it's literally one of the worst movies ever made. Now, that's not to say that SR is one of the worst movies ever made, but other than the cinematography and some of the special effects, that movie literally has NO redeeming qualities in my book. Terrible writing, terrible dialogue and sh**ty acting across the board. And the reason that all makes it worse to me than a piece of crap movie like say, U Got Served, is because it took a character that I really care about and made him as dull and uninteresting as possible. It made Superman into a background character incapable of doing NOTHING other than lifting giant set pieces.
So, at least in my book, MOS would have to make me want to claw my eyes out to be worse than that.