free PlayStation Plus downloads are considered. [Update: Sony has confirmed that PlayStation Plus downloads were not factored into this list -- this list is all sales.] Following The Simpsons is Gotham City Impostors and House of the Dead 3, according to the PlayStation Blog.
With the launch of the PS Vita last month, Sony is now ranking downloads for that platform in its own specific, monthly list. Escape Plan was the most downloaded Vita game for the month, followed by 3G freebie Super Stardust Delta and Tales From Space: Mutant Blobs Attack.
Hit up the PlayStation Blog for the full list.