I'll try to elaborate a little:
The general tone of the thing felt like Episode III, to me, more than anything. There's a sense of personality lurking just under the surface, and once or twice it made itself actually apparent, but for the most part, this was a super-formal, super-serious story about heroism gone wrong.
Also, the pacing is completely shot, and there's no sense of release at any point. It's all punishing buildup that climaxes in ultimate punishment.
THAT SAID
I really did like how blatantly sci-fi it was, and the action was fucking astounding. Henry Cavill was rock solid, and the actors did their damndest (as did Snyder) to lend all this otherworldly craziness some personality and humanity.
It's just that Goyer damn sure isn't allowing for anything but portentiousness. That's Goyer/Nolan, through and through. In fact, when it was announced Goyer was writing, I IMMEDIATELY had reservations because looking at his filmography - dude does NOT know how to have FUN if it isn't dark-edged, angry "fun." He just doesn't. And that follows here, too.
Snyder is trying so damn hard to imbue the whole thing with the sort of sentimentality and emotion that it obviously NEEDS, and he manages to score a couple moments, but they're fleeting, and they never last as long as they should, nor do they stick as strongly as you want them to. Again - I don't blame him, because I really feel they wouldn't exist AT ALL if he hadn't shot them the way he did.
My problems aren't with the story/plotting, or even the conception of this particular Superman. I don't mind his characterization, and the things he does that seem "un-Superman" feel that way in the same way Batman felt a little "un-Batman" in Begins. There was plenty of reason for him to do what he did, and I never felt like the character was betrayed at any point.
It's mostly that the tone is stilted, the pacing is stilted, and there are too few moments where the film feels like it's legitimately alive. It's detached and it's cool, with a hurting heart under that S that beats very loudly.
I guess if I had to letter grade it? B-
I hate letter grades, though.
And that's why I said "Man of Steel is easily the best of all the Star Wars prequels."