For those who are skeptical because you have played these songs before need to know that the gameplay is new for all songs. In career, you only need to play a select number of songs to unlock the next section, so at first I was only playing songs from the older games that I haven't played in a long time and skipping songs that are available on current games such as Guitar Hero World Tour and Rock Band 2. To my surprise when I did finally play those songs that the fingerings for guitar/bass are different. They didn't just take the current guitar gameplay and plop it into this game. Instead, they have updated the gameplay to not only have different fingerings (that in my opinion are mostly a vast improvement over the previous versions of these songs) but they also incorporate the newest styles of gameplay, such as three string chords & the three string hammer-on chords that we saw with the latest versions of guitar rhythm games. It makes all of these previously released songs fresh, new, and fun to play. Also, all the original artists are here, so all the cover songs from past games now have the original artists.
Being able to play drums and sing was enough to make me want to get this previously released material, but having new guitar fingerings for all these songs was a bonus I didn't expect. You also get all the online options from the currently released rhythm games.