There's a very good chance this film might actually surpass Begins.
Sure, Christopher Nolan's first Batman film was a real knockout but there's really a lot of room for improvement. One of the things that really makes me hopeful for The Dark Knight is that Jonathan Nolan is writing and Goyer isn't scripting anymore. That means less corny dialogue and there won't be any problems of over-exposition in this one.
Secondly, I'm sure all the actors from Begins who are coming back (most notably Bale) have looked and scrutinized their own performances and hopefully have learned what does and does not work and will hopefully build on what they have learned from Begins. The same goes for the director as well - Nolan now probably has a much better grasp in handling big-budget blockbusters like Batman Begins as opposed to his experience primarily in smaller, more intimate films. And if I might add, after many repeated viewings of all of Nolan's films, I've come to the conclusion that Batman Begins, although amazing, is still not close to being billed as a superlative example of Nolan's talents, because judging from his previous work he can still do so much better as Memento was an infinitely smarter film while Insomnia had tighter performances.
The third thing that makes me excited about The Dark Knight is that it's been said to be darker than Batman Begins. Sure, Begins was excellent but occassionally some of it's humor was misplaced as well and it's nice to hear that the writers are most probably aiming for a more serious and sober tone for the sequel. Heck, if what Nolan has said about his choice of the title is any indication, we're in for some good times.
And fourth, as in any sequel, there is the obvious hope of seeing a lot of technical improvements over it's predecessor - such as the batsuit, the Tumbler (even if they don't really change it per se, they most definitely would be trying to make it even faster and more maneuverable), better fight choreography and action scenes and things of that nature. I also believe that now Hans Zimmer and James Newton Howard have gotten used to playing off each other's styles after their collaberation in Begins, they can really up the ante for the sequel. Just like how many believed X2 and Spiderman 2 were a big step up from their originals, it's not that hard to see that the hopefulness of many fans in the case of this franchise is not misdirected.
And last but not least, the amalgamation of all these factors that gives off the same feelings of positivity that many of us experienced when Begins was being made. From what we've been hearing so far about The Dark Knight, it really isn't that surprising. Everything sounds damn sweet. Sure, ultimately our own expectations with this film might outgrow reason and overshoot the limits of reality and we'd be pissed because regardless of how good it is, it didn't cure cancer and wasn't the second advent of Christ like we all expected. But then again, it's part of the pains one has to endure for having such a deep and vested emotional interest in something.
Regardless, when it was all said and done, all that anticipation for Begins did pay off in the end (even if many of us weren't
completely satisfied with the final product) and that is why we are here hoping that lightning strikes twice (and even harder this time) for Batman.