“Over the past 75 years, the Superman symbol has been rendered in a wide variety of styles…”
In almost a century, the Superman logo has been changed over and over… sometimes more than once in a year, other times, more than 40 years were between one change and another, –for example, the huge gap between 1944 and 1986. Man of Steel #1 was revitalized and resurrected in 1986 and the emblem was very subtly changed, and it wasn’t until ’93 that it was changed again.
And those are just the changes that it went through in the comic books, –in films, it was another story, and the changes weren’t as numerous, but there were still plenty. The infographic can be found by clicking through the source link, it’s really great, and totally informative. For example, it’s theorized the 1978 logo worn by Christopher Reeves was handsewn by one of the characters in the movie, which is why the logo was so sloppy looking.