TIH could have easily been a sequel. In fact, I personally consider it one.
I do the same thing, personally. Of course I'm a big fan of the Ang Lee movie. However, if one just ignore that one scene in the opening credits, it all fits pretty well.
Anyway, on the topic at hand. I find it a little difficult to answer this question if only because it's asking what the "most intriguing" movies never made were, which is a different animal altogether than movies that I most wanted to see that were never made. For instance, I think the development process of
Superman Lives! and the movie itself is incredibly interesting to read about (I mean, c'mon, K? Lexiac? Superman not flying?) but there's no chance in hell I actually would've wanted to see the movie actually be released. The same goes for James Cameron's Spider-Man script with Carlton Strand and "Boyd."
Now, as far as stuff I would want to see?
My vote goes to Raimi's Spider-Man 4. Not with studio interference, though. I'd want to see what Raimi would have done with it if he was allowed free reign. Of course, I'm a big Vulture fan, so I'm still let down that he was robbed of his chance to be in a movie, aside from just being annoyed about this reboot nonsense altogether.
Another superhero film that never happened which is interesting to think about (though again, I'm glad it didn't happen) is the New Line version of Iron Man, that the Smallville guys wrote at least one draft for. It had a younger Tony Stark and pitted him against his father, Howard Stark, who would suit up in a War Machine armor at the end.
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