Two schools of thought persist regarding how video game sales will respond to the recession-leaning economy.

The first says sales should remain stable as Americans opt for at-home entertainment to save money, and video games last longer and are more engaging than movies or TV.

The second disregards such optimism, insisting video games will suffer along with everything else when people pinch pennies.

Thursday’s report by market analyst NPD suggests the latter could be likely.

Game sales dropped 7 percent in September from a year ago, the first substantial decline since March 2006, with games, hardware, sofware and accessories pulling in only $1.27 billion, NPD found.

Yes, only $1.27 billion, on projected sales of $22 billion for the year. Software alone fell about 6 percent in September, and hardware dropped 9 percent.

Among games, “Star Wars: The Force Unleashed” topped the sales charts for the month of September, with maker LucasArts moving 610,000 copies for Xbox 360 systems, 325,000 for PlayStation 3 and 223,000 for Wii. Hardware-wise, the Wii was top seller among consoles last month by a large margin — 687,000 units in September — compared to 347,000 Xbox 360s and 232,400 PlayStation 3s.

But NPD analyst Anita Frazier told Reuters news service that the September decline could be dismissed as minor. A year ago, game retailers were rocking in the wake of the monstrously popular Bungee-developed shooter “Halo 3,” released last September. That game helped boost September 2007 year-over-year sales 75 percent.

So the naysayers may have to back down a bit — for a month, at least. If sales figures continue to slide even a little, even with the holiday shopping season approaching, then the video game industry may not be the recession-proof monster many had hoped.