No total reboot.
Here's my recipe for a blockbuster Supes film:
1.) Absolutely keep Brandon Routh. It's NOT his fault that Superman Returns was so dour.
2.) Keep all the cast except Kate Bosworth as Lois Lane -- maybe replace her with Parker Posey.
3.) Get rid of the kid; pretend he never existed
4.) Introduce Darkseid, Brainiac, Metallo or Doomsday as the villain
5.) Kevin Spacey was great as Luthor, but I think Luthor should either not be in the next one or -- or have a much reduced role (which Spacey would probably not go for)
6.) Keep the John Williams theme (I can't imagine Superman without it since 1978 -- it's become part of the character as much as the Alexander Courage TOS theme is Trek and John Williams Star Wars Theme is, well, Star Wars)
7.) Keep the same production designer
8.) Either keep Bryan Singer or get Richard Donner back to direct
9.) Keep it FUN! Not campy -- there's a difference!
10.) Add much more action! Superman -- The Movie had ten times the action of Superman Returns. Use that as the template!
11.) Do NOT go too dark! Superman Returns was actually kind of dark to me. Learn from the Trek TNG movies (Insurrection and Nemesis)! Two dark movies in a row spell doom for a film franchise! And this is not Batman -- nor should it be anything even remotely resembling it. Superman is a hopeful and larger than life character.
All of the above = guaranteed box office blockbuster!