Personally I think Nolan did a lot of right with Batman, but always have felt Snyder falls short when its about things other than visuals and Goyer didnt convince me a lot with his script for Batman begins, that suffered in the dialogue department.
Man of Steel starts just wonderfully. Krypton is portrayed like never before, theres a lot of emotion in those first scenes. And Clarks childhood is even better when you consider this is groundbreaking, as little has been developed as to how all those super-powers would affect a child that considers himself normal. This is when you thank for this new tone Nolan and co. have brought to the genre. Maybe its just me but this movie pays homage to Donners films more than once (specially when its about what both Jor-el and Jonathan Kent, sometimes literally quoting his Donner-verse predecessors) only this time it is with a twist that makes everything feel more serious, more expanded. Also the script is basically STM and SII events put together. But no problems there, believe me.
So, whats the problem? What is that most critics seems to have a problem with? What is the fun thats missing? Thing is, when we get to see Superman in full costume after a wonderful and promising origin story... the movie forgets this is a Superman movie and goes directly to an alien invasion film. Just when this normal man is prepared to presents himself to the world, do wonderful deeds, leave everyone in awe, nothing happens and were taken directly into a complicated Kryptonian invasion that completely removes all those iconic moments everyone is expecting. Superman, the character, is introduced to the world only in function of the Kryptonian invasion and his heroic deeds are skipped until the end of the film. So, basically the world and this is a group of soldiers and FBI agents and Lois Lane, not the whole world knows of Superman after they know about General Zod and his henchmen. And so, Superman the character, is left incidental to the plot. One important character but not the quintessential superhero as he should always be. He could be easily described as the "first Kryptonian."
To make it worse, Lois Lane takes no time to find out about Clark Kent and his super powers and alien nature, of which not only a group of people know, but the whole town of Smallville. And all this before Clark Kent even think of going to the Daily Planet, radically changing one of the core elements of the myth just like that. I get that a TV series such a Smallville which premise was having a superhero show without the superhero, one of the stupidest concepts Ive ever heard go and change everything so they can keep making episodes avoiding the full costumed hero. But for a movie that promises the real deal, lots of what Supermans story is was changed for no important reason.
The acting is very good, Cavill does great as Clark/Kal-el, Shannon is also great as Zod, Amy Adamss Lois Lane is also a surprise as this version is much more than the usual nosy shallow reporter and Russell Crowes jor-el is also notable. The rest is also good as most secondary characters are given something to do. Special applause to Kevin Costner and Diane Lane. The special effects are incredible but after a while they end up being more tiresome than actually surprising.
In short, this movie had everything to be outstanding, but its tone predominated over and digressed just when it was most important to have kept some fundamental elements. Or, if you know little of Superman, you can enjoy this much more as an awesome alien invasion movie.