According to over 2,000 developers in North America and Europe who were polled in the 2008 Game Development survey, the Xbox 360 and pc are their main platforms to develope games for: http://www.gamedaily.com/articles/ne...lopment/?biz=1
The 360 isn't a surprise considering the huge US installed base. However, the pc is a surprise considering how slow sales have been during the last few years. And also, despite the Wii being the over all console winner this generation---it was in last place as far as which systems the developers chose to make games for first.