Good points, but think about this: They didn't even attempt Batman Begins until 2005, roughly six years after the craze started (or three, if you want to say the starting point is actually Spider-Man, which is arguably a better starting point). Take into that the development time and size of Superman Returns, as well.
This probably goes back into what BL was saying about being restricted to a single studio, but still, it seems like they really wasted all these years not pulling some kind of investment into other non-Batman/Superman projects. I can understand them not wanting to start another large scale tentpole franchise with a lot of their budgeting being tied to Potter, but it seems they still had more than enough resources to try other properties with smaller budgets with so many other films based on superhero properties doing as well as they were.