The two biggest music releases of the year aren’t albums: They’re video games. Guitar Hero may well be this decade’s biggest rock & roll phenomenon. Guitar Hero I and II have grossed $360 million since the first game came out in 2005 — vastly more than any album released in the same period. And the games — in which players re-create songs’ guitar parts by pushing buttons that correspond to notes and chords while hitting a “strum bar” in rhythm — have inspired kids by the millions to memorize the intricacies of “Free Bird” and “War Pigs.” Rock Band will offer entire albums for download, including Who’s Next, as well as eighteen songs by the Grateful Dead.