Activision must have been under tremendous pressure to develop an empirical method of determining the greatest songs in the Guitar Hero series for Guitar Hero: Greatest Hits. It would be difficult to pick the determining factors: fan votes? Number of notes? Length? Sales as DLC? Sales of the original record? Some kind of measure of volunteers' brain activity while playing? It's a big question. And what if songs came out after the release of the collection that were even greater than the Greatest Hits? Then the title would be a lie!
Activision's solution: change the title to Guitar Hero: Smash Hits. That's safe from potential inaccuracy, because it doesn't really mean anything!
That "The best of Guitar Hero music" line at the bottom kind of ruins our theory about the name change. Ignore that part.