I'm a Nintendo fan first, but it doesn't really surprise me to see the HD consoles get the Western attention. Nor do I believe in crazy conspiracy theories like a lot of Wii fans. These are the reasons I see:
1. As pointed out in the West PS360, together has a higher install base than the Wii. In terms of game development, at this point for a third party the PS360 basically appear to be a single console with greater marketshare.
2. A large portion of the Wii install base aren't traditional gamers (I refuse to use the term "casual" because it is so meaningless). A developer can make a game for the PS360, and be at least reasonably confident it will sell because the market is better known. Sometimes, however, they miss the mark horrendously (*cough*bioniccommando*cough*). The Wii has a traditional base, but it is an unknown, but significantly smaller portion of the whole.
3. A significant portion of traditional gamers who own a Wii also own a 360, PS3 or both. The result of this is if devs make the Wii version of a game watered down, those people will likely buy the PS360 version.
This results in it basically being less effort to make a successful PS360 game. The non-traditional gamers that Nintendo has brought in still haven't been full figured out by the market, so most games targeted at them verge on shovelware both because of a general disdain and lack of respect for them ("lol, casuals love crappy games") and because companies are sort of probing to find out what sells. When a company does hit gold with an effort that's more than just half or quarter-assed, it sells very well, for a very long time (Mario + Sonic, EA Sports Active).
Basically, the TLDR is this: the PS360 are less risky. HD gamers are a better known quantity, and thus less risky.
