I think Frank Miller had no idea what to do with the material. So he made up a bunch of crap that the actors then had no idea what to do with.
The original Spirit comic stuff is fairly straightforward stuff. The movie is just total crap.
I dunno
Yeah I know the scale of things, the degree is vastly different, but conceptually its roughly the same idea so - given the radical departure the X-Films have been from the source material - it doesn't seem a major leap to me.
Personally, I thought it was a fun film. Not X-Men or X-Men 2 level, but better than X-Men 3. A fun straight forward blow stuff up action film. Its very much Commando with Mutants though.