I think you can get progression and a solid continuity when you have the same group of people making the books for a long period of time... during the 88-99 period it was basically the same bunch of dudes, with people coming and going at times. Then, Loeb's team came around and they also kept a consistency within their crappiness for as long as they lasted. There's no doubt that the characters they were writing were very different from the Jurgens era ones, since they were less realistic and more Silver Age inspired. They made some pretty big changes to make the show more like the animated series, and then Smallville.
Since then, no writers have stuck around for too long, so obviously that means there's no consistency in the characterizations (which isn't necessarily a bad thing). Tomorrow a new definite team of writers could come along and develope the characters for the next 20 years.
And by the way, SR doesn't qualify as a "box office disappointment" in any sense... it just didn't do as extraordinarily well as the studio hoped.
