Jerry Bruckheimer is a Producer
Gale Anne Hurd is a Producer
GARY KURTZ is a Producer.
In a nutshell a Line Producer makes sure everything gets done on time and and to budget while negotiating other locations in the shooting schedule when things go pear-shaped. Rick McCallum is extraordinarily capable in this role but to be a producer you have to have these skills plus the skills of a creative talent. (Good) Producers are the glue that hold a project together, they can offer helpful suggestions on shots, character, story, location, Actors etcetera. A good producer is sometimes more responsible for a finished film than the Writers or Director/s. In the case of large studio films where the producer shepherds the project through all stages of development he or she is often more integral and less replacable than the chosen director.
In this sense George Lucas is the real producer these days having stepped up his role from Executive Producer on the OT after he parted ways with the enormously talented Gary Kurtz. (Seriously if Kurtz had produced the PT film no-one would have any complaints.)
But the credits on LFL films have always been iffy as GL's not a member of the DGA or the WGA and so can choose to create credits or omit them at will. This is the case with the writing credits on ANH as much as with yes-man McCallum's overblown position.
By the way if anyone doubts that Gary Kurtz would have saved the Prequel Trilogy from farce and the weight of its own hubris then they are either ill-informed or just plain kidding themselves.
Now onto Superman, the latest casting rumour appears to have one-time Superman contender Jude Law taking over from Terence Stamp as General Zod, (or perhaps a relative? Gog??)