This is for the U.S only but you can expand it out to the western market in general.
When the Xbox 360 was released in November 2005, Activition and EA came out with ports of their popular ps2 titles Call of Duty 2 and Madden 06. Despite the PS2 versions of the games selling millions, the X360 versions were able to sell respectable amounts with COD2 having a close to 90% attachment ratio for the new X360, madden with over 50% . At the end of the year the X360 sold about 563K units in the US and had 18 games in the top 100 most 3rd party (call of duty was at 500k for the 360, 264k for madden 06).
Fast forward 6 years and EA and Activision again came out with their big titles this time for Wii U; Madden 13 and COD BO2. The attachment ratios for both games are atrocious despite the Wii U having twice the userbase of the X360. 1 million Wii U (for end of year 12) vs 563K X360. And only 2 games show up in the top 100 at the end of the year for the Wii U no 3rd parties (no games except 2 in the top 100 for 4 weeks and counting)
Looking into 2013, why would either company commit any resource to the Wii U versions of their high selling games? I mean, the PS360 versions will out sell them, do they make the games on the PS360 platform to try to save money and alienate Wii U customers or do they build on the next gen platforms and waste money they will not receive back since the development cost will be so high?