Ignore for a moment the effervescent pop hits “In da Club” and “21 Questions.” What 50 Cent really brought back to hip-hop in 2003 was melancholy. Most of his debut — songs like “Back Down” and “Many Men (Wish Death),” which saturated urban radio without poking through on MTV — played like thug lamentations of the highest order, haggard and grim.

Considering how successful 50 Cent was last year — selling 6 million albums — he’s earned the right to the glamour-happy, brand name–dropping “Stunt 101,” the first single from his extended G-Unit family (50, Lloyd Banks, Young Buck and Tony Yayo, who is unable to tour because he’s in jail for gun possession). As on 50’s breakthrough, though, that single belies the darkness of his group’s debut.

Peel away the rote celebrations of glimmer and girls (“Smile,” “Baby U Got”), and 50 & Co. sound just as preoccupied with the streets. On the run-of-the-mill revenge tale “Eye for Eye,” 50 inveighs against the haters: “I’ll blow your brains on my New York Times/Run off/Turn to the sports section and read your mind.” On “G’d Up,” a stark Dr. Dre beat — employing tolling bells and mournful piano — carries lackluster verses from the crew.

50’s signature wit is notably absent, so the fate of G-Unit hinges largely on his posse. On the James Bond–style title track, Banks matches humor with violence: “We tired of you niggas with your maybe beef/We gon’ be here forever/You temporary, like baby teeth.”

On the excellent “Footprints,” where producer Nottz expertly chops up a gospel sample and flutes, Young Buck proves fiery: “Every day’s a death threat/But I ain’t dead yet.” It’s that resilience that made 50 so compelling and makes Beg for Mercy, at its best, play like a document of struggle, not a celebration of success. Hunger becomes them.