Batman: Arkham Asylum has been a critical hit ever since its launch in late August, and was one of the big surprises in yesterday s NPD sales data release for the month.

The sales chart, led by obvious leaders Madden NFL 10 and Wii Sports Resort, shows Batman’s two SKUs placing fourth and fifth, with Xbox 360 edging out the PS3 version by about 13K units.

In total, a half-million Batman units have been sold, with a strong September showing now expected. The marketing is well targeted with a hot franchise and, most importantly, a high quality product that led to significant word of mouth. We will examine Batman: Arkham Asylum in an upcoming the[a]listdaily feature.