I thought it did come across as quite boring, especially for a Superman/superhero movie. Ebert's comment that the action seemed 'dutiful rather than exhilarating' is how I felt - the action scenes seemed long, laborious, a bit pretentious, stylised and not always very well filmed.
The scene where Lex's henchmen beat up Superman is particularly odd and seemed 'wrong.', in my view. There is no attempt to fight back verbally or physically - and while Singer obviously wanted Superman to suffer (like Christ) and then be stabbed in the side (like Christ), and while some people will like that scene for showing Superman at his most vulnerable - I think it struck the wrong tone.
The plot does have issues, which have been raised here over and over regarding Superman's silent absence, Lois's pregnancy and the timescale of her meeting Richard. I can forgive the plot convenience of the museum just happening to have a mineral exhibition that just happens to contain kryptonite (Lex reads the article in the paper when standing on the steps of the mansion) just as Lex is free and Superman is back.... although I'd rather the museum hadn't had a special exhibition, but instead was routinely displaying minerals (as many museums do).
Lex's landmass plan has been questioned on here too - it was obviously done to bring something epic in scale. But they then had to stretch Superman's powers to be able to lift it into space, after hovering for a second in front of the sun to charge up. One wonders why he wasn't sent to a tanning salon rather than a hospital when he fell from space and amost died! A sunbed would have done more good than a hospital bed!
There also weren't enough characters to make this work correctly as a story. No one filled the mentor/guardian/elder archetype properly (as Prof Xavier, Obi Wan, Ducard, Gandalf, Aunt May all do), as Jor-El was an inert recording and Martha had a tiny role. And the emotional core of the story (Superman himself and also Jason) was problematic and poorly explored.