What I find interesting, whether it be in regards to "Superman Returns" or "Smallville" or anything Superman related for that matter, are complaints from fans about certain aspects of the Superman mythos that they feel are non-negotiable. Yet most times these aspects aren't things that have necessarily been there for long at all, but because they've grown up with that aspect of the mythos, they won't accept any variations to it.
I'm not explaining myself very well so let me give you some examples of what I'm talking about...
The Kents... alive or dead? Due to events in Season 5 of "Smallville", many fans have called into question just what the proper status of the Kents is. In the Golden Age of Superman comics they passed away without much fanfare. In the Silver Age comics they both died within a short span of each other from a rare disease when Clark was still living in Smallville. In the current comics they're both still alive even though Clark is a grown man living in Metropolis. In "Superman: The Movie" Jonathan Kent died of a heart attack when Clark was still a teenager. Martha died an old woman years later (as told in "Superman III"). In "Lois & Clark" both Jonathan and Martha are still alive.
So, as you can see, there's no "proper" way. No way it's "supposed to be". It just is whatever the current telling of the mythos decides it is. Whatever best fits the story being told.
Another example is the "S" shield on the cape. Some fans have called down curses on Bryan Singer and the costume designers because it's not there on the "Superman Returns" costume. Well the fact is that there was no cape on the original costume as drawn by Superman's co-creator Joe Shuster. There's no "S" on the cape in the Fleischer Superman cartoons of the 1940s, nor on the cape in "Superman: The Animated Series" or the current "Justice League" and "Justice League Unlimited" cartoons. Even when it is on the cape, it hasn't always been the same color or size.
And what of Superman's arrival on earth? Surely that's set in stone? Nope, sorry. Not at all. Over the years, throughout the re-tellings of Superman's origins, it's true that most times Superman arrived as a baby in a rocket. Some times he was found by the Kents (be they Jonathan and Martha, or John and Mary, or Eben and Sarah). Some times he was found by an unnamed elderly couple and dropped off at an orphan asylum/orphanage. In the 1940s Radio Series he came to earth, emerging from his rocket as a fully grown man.
Many people will say, "It's not the costume that makes Superman who he is, it's his personality. The fact that he chooses to do the right thing simply because it's the right thing to do". And that's pretty spot on in my opinion. But even Superman's personality has changed over the years and his manner of fighting the never-ending battle hasn't always been the same. The original Superman, written by his co-creator Jerry Siegel, had no qualms about beating on wife-beaters (Action Comics #1) or allowing villains to commit suicide (November 1941 Superman newspaper strip).
I could go on and on about various aspects of the character's look, his family, his life, and over all history and how there have been differences and variations over the years.
Both "Smallville" and "Superman Returns" take many cues from the Christopher Reeve films, but neither are direct sequels or prequels as the case may be. Both also draw inspiration from the comics (both new and old), but don't keep strict continuity with them either. Both are their own version, and stand alone while still being a part of the character's over all evolvement and paying tribute to past incarnations.
Nothing is set in stone. Nothing is "supposed to be" a certain way. It just is what it is. As Brandon Routh said during the WonderCon 2006 press conference: Things don't always change for the worse, sometimes they change for the better.
I'm not saying you have to like every version of the character or every change that is made to him in whatever medium he's perpetuated in, but just be aware that he hasn't always been nor will he always be what you think he is or should be.