(Wall Street Journal) — A year ago, top Gap designer Patrick Robinson stood alongside Oprah Winfrey and Vogue Editor Anna Wintour at the Metropolitan Museum of Art overseeing the New York fashion industry’s most prestigious gala. Thursday, he was out of a job. His departure after four years of lackluster results was yet another sign of Gap Inc.’s failure to breathe new life into its namesake brand, which peaked in the mid-1990s. It also underscores how difficult it can be for a retailer to set itself apart with jeans, T-shirts and other staples that can be found everywhere. Mr. Robinson’s appointment in spring 2007 received considerable fanfare. His resume boasted stints at Perry Ellis, Anne Klein and Giorgio Armani, as well as a degree from the Parsons School of Design. He was named one of Vogue Magazine’s 100 rising stars in 1996. Mr. Robinson notched some successes, including a revamped line of jeans that was critically and commercially well-received. But overall, improvement didn’t materialize. Same-store sales at Gap brand’s North American stores declined for 14 of the 16 quarters of his tenure.