Hmm...from the point of view of never having been a comic/superhero fan at all, and having come only recently to sort of like Ben Affleck in his own right after having felt for some time that he was somewhat riding on Matt Damon's coattails, and Hollywood initially trying more to "make him happen" because he was the more conventionally handsome of the two, I could actually sort of see this working.
Probably not for the hard-core comic fan, but there's a certain "fit" there to my mind. And if the movie is well made, it could potentially do every bit as well among those who might be interested in another take on a familiar character as it would by catering strictly to the comic aficionado. I think there are more of the former among the ranks of movie-goers out there anyway.
That being said, I don't watch many movies at all, and those I do enjoy are overwhelmingly those in which the screenplay is the selling point rather than anything in the way of action/special effects and such. So the conventional Superman movie probably wouldn't appeal to me to begin with. Who knows but that a more introspective take on a slightly older Superman might not fit the bill?