Credit Suisse analyst Gary Balter called the Amazon development "disconcerting," suggesting that it chips into a kind of monopoly that GameStop has on used games, albeit one too small for game trade-in competition from Amazon to have much impact on the specialty retailer's profits.

GameStop profit margins have benefited from an active trade-in system in which shoppers return used games for a fraction of the purchase price or store credit. The returned games are sold at a higher profit margin than new games.

Balter suggested that GameStop can withstand near-term encroachment from physical retailers.

"That (Toys R Us testing) in many ways is less of a threat, as GameStop's advantage of 10 times as many locations and selection seem to make them less vulnerable," he said. "Best Buy and others have tested it for some time but have not been as successful."

GameStop this month reported a 22% jump in overall sales and a 10% increase in sales at stores open more than 12 months for the holiday sales period ended Jan. 3. It didn't hurt that videogame sales climbed 9% in December to a record $5.3 billion, according to market research firm NPD Group.

GameStop's sales gains are particularly buoyant compared with other retailers that sell videogames. Best Buy Co., the nation's largest consumer electronics chain, said earlier this month that its sales of entertainment goods, including videogames, movies and music, plunged 12% in December from a year ago. Best Buy's sales of videogame hardware and accessories fell by a "mid-single digits" percentage last month compared with the year before. Circuit City Stores Inc., another retailer of consoles and games, last week announced it would liquidate its 567 stores by April.

GameStop, however, "significantly increased sales of both new and used games," said Daniel DeMatteo, chief executive of the Grapevine, Texas-based retailer in an interview. Results for the final quarter are due in mid-March.