The first part has a title that sounds like a 4th grader made it up.. "Batman Begins"... and then the second film has something mysterious, slightly gothic, and serious in its title called "The Dark Knight"... "Batman Begins" - "The Dark Knight" just doesn't have any titular compatibility! I'd be happy if it was just "Batman: The Dark Knight" that would give some continuity... or if the first film was called something like "Rise of Vengeance" THEN would "The Dark Knight" fit in. All right...
And does calling the second one Begins make any sense at all, considering the fact that it already began?