Random essay on my opinion because you all care:
The appeal of Batman Begins is its 'realness'. It tries to take a more plausible approach on comic book heroes and thereby better appeal to our generally cynical, skeptical, and empirical modern society. Instead of Batman swooping in to save the day and deflecting all hopes of intervention by most criminals, the Batman of Batman Begins has to start from the ground up and you see his poor first attempts and the harships he undergoes to become the hero you see in later appearances in the Gotham universe.
Personally, if I am going to see a film about comic book superheroes, I expect it to be, to some extent, over-the-top. It's interesting in its own right to see entities with certain abilities/powers battle it out without the constraints of reality: we go to the cinemas ostensibly to *escape* the rules of reality and society, not to have them subtly imposed on us even more (despite how much this may actually happen...). With a film like Batman Beyond, these rules are pretty blatant. The Scarecrow's 'power' is explained in some whiffs of science. It seems that writers expect audiences to be a bit more mature and discerning when it comes to the willful suspension of disbelief because we live so often in fantasy nowadays that it can be difficult to make the distinction between fanciful film and the real world.
I could enjoy a film like Electra which may have had a relatively insipid plot in that it wasn't something "unique" or compelling but still had some cool ideas, powers, fight scenes, etc. That's what I'd read a comic book for when I was younger, and that's still why I'd see a comic-based film. I think this "realism-shift", in addition to trying to appeal to an aging original target market (kids who read comics who have now grown up), is trying to draw new audiences in with more plausible trappings. I don't think, however, that the appeal of films like Batman should lie in the idea that "whoa, this could happen!", it more lies in the messages that the films/comics convey and the general entertainment factor of seeing otherwise unbelievable feats with your own eyes.