Re: "Superman" or "The Superman" ?
I'd have to watch Nolan's trilogy and keep a score card for how many refer to it as The Batman but in a sense calling him "The Batman" just reinforces the image of fear and urban myth that Nolan tries to create in the films, instead of thinking him as a person the criminals think of him as a thing.
That doesn't work with Superman since he doesn't seclude himself and helps Metropolis law enforcement.
A few of the Marvel Superheroes are somewhat niche characters that aren't extremely versatile, thus they don't have a lot of longevity potential. For example, Namor is a water guy, Silver Surfer is a space guy, Dr. Strange is a magic guy, and so on.