Hip-hop's latest battle between two of its biggest egos — Kanye West and 50 Cent — has been building like a title fight in Vegas. Before the Tuesday release of their respective CDs, "Graduation" and "Curtis," 50 challenged West to a televised debate, called him a "worker bee" while describing himself as a "boss," and vowed to retire if West outsold him during their debut week. In response, West has mostly downplayed Fiddy's bluster, re-channeling it as added publicity for his own release. The two share a Rolling Stone magazine cover posed nose-to-nose, evoking the great showdowns of our time.