I don't understand why they say that "Japanese RPGs aren't as successful outside of Japan".
Based on VGC numbers, most JRPGs sell better in Americas than in Japan.
Quick examples on the PS3 are the likes of Atelier Rorona, Demon's Souls, Disgaea 3, Cross Edge, Trinity Universe, Last Rebellion, Eternal Sonata. Wii games like Pokémon, Fire Emblem: Radiant Dawn, Arc Rise Fantasia, Rune Factory: Frontier sold better in Americas. All 360 JRPGs I know sold better in Americas (that's more than 20).
I guess they are looking at sales relative to market size and from that point of view, JRPGS generally aren't all that successful outside of Japan. If they consider the Dragon Quest series as well, then it's even more lopsided.