Ultimately, it comes down to which console maker is providing the most incentive to the companies, and they are responding accordingly.
Sony is trying to defend the archatecture. The issue is, that Sony has provided little, if any incentive to make exclusive 3rd party games on the platform - a stark contrast from the PS1 (easy development, great storage capacity, strong desire to grow), PS2 (huge marketshare allowing for near-certain profits).
This time around, Sony has given devs the 1-2-3 screwjob. The hardware, although powerful, is far too advanced for a typical studio to utilize the technology in any advantage over the 360 for many years, until studios are large enough to support 300-400 people per game (and costing $30m or more), or Sony provides enough help on the dev side to allow for much more efficent use of the cell to render a large advantage in capabilities over the 360, without increasing costs (unlikely.
2ndly, Sony has not given devs a financial incentive to make a game console-exclusive. I am sure to Capcom, SE, Namco et all, it was the obvious choice on which console to garner most exclusives, as PS2 always led on userbase, therefore was the easiest to get investors and managers the go-ahead, as many many games did well on the PS2 platform, even though the archatecture wasn't nearly as good (dev wise, no regards to power), as the much easier GameCube, and more advanced Xbox.
Thirdly, MS is offering more end-game support for franchises, which I believe, is, and will be, a huge boon to developers, and hopefully smaller ones in the future. When a company like Epic, Bethsada, or Rockstar, are able to create and distribute trailers, demos, and pay-for content for their games, they are given a huge incentive. Sony does have some of this, but since MS has about a 4 year lead (with the 1st Xbox), they have invested far more money, time, and effort into building such a huge userbase for the content (somewhere around 5m connected users by now, all willing and able to buy, and view the big companies content). Financially, this is important for companies to sell extra content like Shivering Isles for Oblivion, and extra content for Grand Theft Auto, as most of the content is made on the cheap (somewhere around 10% of the staff needed to create a game is needed for the extra content). This allows for millions of dollars to flow into their pockets, and keep a virtual presence and sales for even the most weak of games.
I'm merely comparing this in a PS3-X360 sence. Obviously many of these rules apply for the Wii. The userbase is growing, and is large, the cost of developing a game is cheaper, but #3 isn't there, and won't be for many years (even vs. the PS3), as Nintendo isn't really providing for these solutions (512mb ring a bell?).
To investors, it comes down to this:
Spend $20m on a Playstation 3 game, that has a 3.5m installed user base @ 3.0 attach ratio, with only minimal DL content profits
Spend $20m on a Xbox 360 game, that has a 10.0m installed user base @ 5.5 attach ratio and maximal DL content profits
Spend $10m on a Nintendo Wii game, that has a 8.0m installed user base @ 3.0 attach ratio and no DL content profits or availability.
Right now, which one(s) look like the best ones to shareholders? It's obviously the Wii, or 360. The worst, by far, is the PS3. Therefore, Devs would most likely use the 360 as the lead console, and port to PS3, as it'll gladly, and easily cover port costs, and make them money.
Overall, even if a game goes multi-plat, it goes strongly in favor of the 360. Why? Japan. The Xbox had great MP support last gen, and is used to it. But in Japan, it was content starved. With Namco coming full-force with J-games, it bodes well for the 360, as even if hardware sales due to MP PS3/360 games were a 4:1 ratio (which is way too much in the PS3s favor), it still better than the fact that there were none, if any, MP Xbox/PS2 games last gen.
Back from the dead, I'm afraid.
