O RLY?

Most tie ratios for top machines reach 8-12 and Wii is on pace to reach that lifetime. DS had a tie ratio of two through March 2005, which has since grown to 5.5 by shipped figures (536m to 96m SW: HW through Dec 08).

NES, SNES, PS1, and PS2 all had tie ratios of 8-12 by region although SNES is borderline. GC, Xbox also had tie ratios of over 8, so it isn't that surprising to see PS3/360 with big tie ratios.

Usually though the tie ratio does decline as the number of users goes up because its harder to satisfy the tastes of 100 million gamers than it is to satisfy the tastes of 20, 35, or 50 million gamers.

What developers care about is number of games they can sell on a platform. For Wii and DS combined, ~386m games were shipped in the year ending March 2009, compared to ~250m for PS2, PS3, and PSP combined.

There are caveats for both:

PS3 probably sold 75m games for companies besides Sony in the last FY (out of 105m games shipped for the platform), and games like GTAIV, MGS4, Little Big Planet and a few other mega hits take up probably ~20-30% of the total. PS3 games are expensive to make, but it pays off for the mega hits.

Wii had probably 95m games of the 193m games shipped in the March 2009 year made by Nintendo. That leaves only 98m for developers. Still, with cheaper costs to make games and a bigger base it probably is more economical to support Wii. On the other hand, only a few third party games - like Guitar Hero III, Guitar Hero: Legends of Rock, Mario & Sonic, Carnival Games, Lego Star Wars reach mega hit status.

For a bankable, sure-fire 2m+ third party hit, PS3 is probably more reliable for third parties than Wii, but for games which are smaller, potential break outs, or risky the Wii makes more sense.