I've read it and you're right, but "super heroes" had only been around for a year when he appeared, so everything is derivative of Superman. But the main thing is that Judge Hand cited specific panels and combinations of words as being infringement, not just the abstract notion of a "super hero". Erosion of the concept? Or has the concept become "stock"?
A little of both, I'd imagine.
For example, when a character had Superman's powers AND revealed his identity to the reader by opening his shirt, that was infringement. However, when other heroes started doing it as well, it was no longer a (I hesitate to use the term casually, here) trademark of Superman, and is now employable by Superman clones because it's no longer unique to the context.
Likewise, in many circles, Superman is very much a stock character, with Marvel alone claiming at least five characters I can think of that are really, really close. (And heck, going back to the Golden Age, it seems like half of Nedor's characters were indistinguishable from Superman.)
And yes, that's how Hand had to rule. Copyrights are about the details, not the big picture, so it's only a comparison of details--text and pictures--that you could ever say yes or no. If only Fred's costume had been a different color or he hadn't caught that shell in the air...well, Fox wouldn't have bought it, but if he HAD, DC might not have had a leg to stand on.
Ken also rightly brings up Eisner's testimony. However, the court should have seen that as mostly circumstantial, since the intent behind a work doesn't really affect whether or not it's a copy. It does, however, do a great job of coloring the interpretation. I mean, you can't convict someone for murder, for example, if he plans it out then...goes to Six Flags instead. (The episode is also worth pointing out as a testament to Eisner's abilities: Even when tasked with merely copying, he came up with something that's only a hair's breadth away from having been a hit in its own right, unlike Fawcett's Master Man, say.)
That's why I recommended building a new Superman off of the differences in public domain material. The differences add up quickly and scrub out the similarities to what's now considered generic. And, by the way, I'm thinking more about performing the review I suggested; I have a lot of balls in the air, these days, and am on the verge of--gasp!--blogging so people can keep up to date, use things I release, and chip in wherever they feel like. And as I think about it, this is the sort of thing that'd mellow out some of the intense programming projects I have ahead. I'll mention it when it's running, for the interested parties.
Strange nobody's really brought him back, expect that seemingly dead blog (which I think is Brad Spencer, Wonderman from Nedor/Standard/Better rather than the Fox Wonder Man).
The book was supposed to be about the Nedor character, as far as I can tell, with the Fox character making an appearance.
It's possible that the series didn't happen because the Nedor book copyrights only have "one foot in the grave," so to speak, and many could be owned by National Amusements, Warner Brothers, or someone we've never heard of.