I'm not sure why you would dismiss that point so quickly. The WKC games have a lot more in common with Xenoblade and The Last Story compared with Ninokuni. I don't think the majority of consumers judge a game by the developer, but rather what it actually looks and plays like.
White Knight Chronicles 2 came out a month AFTER Xenoblade in Japan, so it's definitely a valid comparison if we're talking about games in the genre across different platforms selling differently. White Knight Chronicles came out, and lots of people didn't like it. But the sequel coming out over a year and a half later still managed to outsell Xenoblade handily.
Xenoblade, The Last Story, and White Knight Chronicles are all first party RPG releases, developed by known RPG developers, featuring a more realistic but still very Japanese art style. They are all also significantly influenced by western RPGs in terms of game design. All three games also came out within the same 7 month period from June 2010 to Jan 2011.
They're totally comparable and any attempt to dismiss it would be unwise imo. It's definitely worth looking at closer.
I think you meant WKC2 in your 3rd paragraph. WKC1 came out in 2008.
I'd agree WKC2 makes for a better comparison, and it sold around 100k more than XBC & TLS each did rather than more than both combined like WKC1.
Rounding up the 1st party console RPGs this gen with Famitsu sales from Garaph:
Xbox 360
Blue Dragon (2006) 203,740
Lost Odyssey (2007) 109,517
Kingdom Under Fire: Circle of Doom (2007) 23,936
Too Human (2008) 8,840
Fable II (2008) 56,197
Mass Effect (2009) 27,397
Fable II (PLATINUM) (2009) 6,480
Fable III (2010) 35,660
Mass Effect 2 (2010) 8,427
PlayStation 3
Folklore (2007) 38,305
White Knight Chronicles (2008) 339,690
Demon's Souls (2009) 168,118
White Knight Chronicles EX Edition (2009) 25,530
Demon's Souls (BEST) (2010) 68,524
White Knight Chronicles II (2010) 249,350
Wii
Fire Emblem: Radiant Dawn (2007) 171,924
Super Paper Mario (2007) 505,491
Captain Rainbow (2008) 22,682
Takt of Magic (2009) 17,350
Xenoblade Chronicles (2010) 141,059
The Last Story (2011) 157,359
Pandora's Tower (2011) 33,845