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!