There was not this much hoopla for the 2000 inauguration. This is likely due to the dragged out election ultimately stolen by the supreme court, and that it was yet another white guy assuming the role of the presidency.
This inauguration is historic for severeal reasons, the most obvious one being that it's the first time the United States has elected an African American. Second, it's hopefully a clean break from the devastation of the past eight years. Finally, this is the first election where the electorate has an intimate role with the election process whether it be through web 2.0, or unprecedented volunteer efforts. Because of this it's likely that millions of people feel as if they played a significant role in helping to elect Barack Obama.
