As one historic duel — the presidential race between Barack Obama and John McCain — ends, another is heating up. The stakes are high: nothing less than the soul of rock ‘n roll. The competition is fierce. And you will decide — with your wallet. In one corner is “Guitar Hero,” the franchise that revolutionized the rhythm-game genre in 2005. In the other corner is upstart “Rock Band,” which rewrote the rules last year by adding drums and vocals to the mix. Several third-party candidates are waiting backstage, hoping that one of the two major contenders hits a false note.
