Have you read SUPERMAN: FOR ALL SEASONS? Or ALL-STAR SUPERMAN? Or KINGDOM COME? Because I think they all make Superman fascinating. I wasn't his biggest fan until these graphic novels came along.Superman is too one dimensional for me as a character.
Offering different continuities isn't enough. I'm not interested in continuities. For MARVEL to compete with DC, there needs to be a constant display of out-of-continuity stories that give the creators complete freedom to allow for MARVEL to move beyond its standard fare and to something more sophisticated. There's very little stuff from MARVEL like that (the closest is Gaiman's MARVEL 1602, which is quite fun).Back to the continuity topic i think Marvel has plenty of different continuities/universes to give the reader a choice.
In the end, I feel like DC simply fosters more sophisticated and creative storytelling by offering more creative freedom by allowing for so much to be done outside-of-continuity. We've gotten such wonderful stories as THE KILLING JOKE, THE LONG HALLOWEEN, ARKHAM ASYLUM, SUPERMAN: FOR ALL SEASONS, etc. In fact, nearly all of the great DC stories have been outside of continuity, since they allow for immense creative freedom and exploration.
The DC characters, because of that, become much larger. They're not as defined as MARVEL heroes. Batman isn't so much a defined person as he is an idea that has taken a variety of different forms. And I love that. I love that these DC characters aren't just redefined when a new continuity comes along, but instead are redefined almost every year. DC characters are in a constant state of flux.