Yeah, like Knox said, they want the movie to be **that** movie for this generation, not for the character to literally be Superman. After all, Wonder Woman is only three years younger than Superman, and she's held her own alongside both him and Batman for all that time. As a character, they don't have to try to make her be like Superman, she just has to be true to the character. That's what they're seemingly hoping to accomplish here, to have that defining film. THIS is Wonder Woman. All previous versions are just imitators, because that's what Superman (1978) did for his character. They want to have one of those moments. WB/DC
needs this film to be that.
For many people, Christopher Reeve IS and forever will be Superman, and whether unfair or not, his portrayal of the character is so iconic that it is the barometer by which all subsequent actors in the role have been judged by.
That's because Christopher Reeve played the role so ingeniously, he brought believability to both the role of Superman and Clark Kent. In fact, it was his portrayal of Kent that got him the role. He played the role so well that you could see why most people wouldn't suspect he was Superman. And, he was the best Superman too. He had the height, the looks and a dye job on his hair made it the right color. Add to the fact that he was working out so much to fill that suit that they had to re-shoot some of the stuff they filmed earlier for continuity's sake. The way he acted embodied everything about the character. And, last but not least, his hang gliding experience made him a natural in the wired flight harness. He brought a believability to the flying that was never there before.
His look was so popular that the rebooted Superman comics in the '80s and '90s often had the character drawn in a likeness of Reeve.