I think the reason I liked Begins so much was because before that, I had not been into Batman that much. Never read the comics, never really liked the previous movies, only truly enjoyed the Animated Series. I didn't know much about Begins at all, and it was just sort of a whim when my brother in law and I went to see it on opening night–he's been a Batman nut since he was 6. I walked in with expectations of a fairly average superhero movie (not thinking it'd be as good as Spidey 2) and what I got was the best fucking origins story I've seen. Honestly, that first hour, hour and a half is just fucking gold. The last parts of the movie are great too, but they aren't, like, OMG BATMAN PWNS ALL NOW BITCHES. What makes it my favorite superhero flick is the first hour and a half.
I'm going into the Dark Knight with high expectations, so that's a scary thought. I sort of hope they would focus a lot on the Joker and why he does all of shit rather than "lolz I'm the Joker you gonna get pwnt," but I don't know how far Nolan and Goyer are taking that. From what I hear from the script, I like it.