It's Fun. Period.
Perhaps those people believe that because they are just used to playing the first game more. In the second game, the music selection tends to include a lot more metal songs, or songs that have excessive screaming in it. However, it also stays true to it's roots, including a wide variety of music from Lynyrd Skynrd's Free Bird, to Beast and the Harlot by Avenged Sevenfold, to selections such as You Really Got Me by Val Halen. This time around, there are much more notes to hit, and the notes will be coming at you at a much faster rate. Ultimately, if you are good at the first game, this game will kick it up a notch. It is much harder and will provide a larger challenge for the truly exceptional "Guitar Hero." If you purchase this game, be prepared to have fun, as well as say goodbye to a small part of your social life.