Analysts have been trying to positively qualify for Sony how these events have operated since the whole PS3/Wii debacle started. The fact is that the unbearably expensive console has always failed. On top of that, we've seen that the systems that are released with about a year of extra time sell well. The result: The PS3 flops. That was obvious. The 360 excels early. That was a given too. The Wii, with it's price, exclusives, and new control was also destined to start strong, like the N64 did with mostly new 3D worlds.
The difference? Whereas Sony had a head start, a better storage medium, and general developer support to power them through their first generation, now they really have none of these. Last gen, Sony had a huge head start, along with untruthful, but powerful statements about power, they were able to defeat the Dreamcast before it launched, while instantly selling out for months, due to the belief that the system is amazing. Essentially, it was able to kill the GC and Xbox, too, solely from the momentum the developers picked up on it.
This generation, the 360 came first, with a strong start, but Sony's untruthful lines about the PS3 and Blu-ray's abilities kept the majority of developers and consumers waiting to see. What happened? E3. People saw that Microsoft had a solid line planned out, the Wii truly had the option to create brilliant control, and the PS3 decided it would be $500 or more, without any major draw beyond the 360. At this point, I think everyone should have seen that the PS3 was going to receive a poor reception, knowing that price does matter, and that the other two consoles both seemed to be doing great.
Now, the Wii looks like it might push past the 360 this year. Why? One part because of the PS3's wait, one part because of the pretty large price difference in comparison to perceived value, one part hardware issues, and one part a slow Spring and Summer for games in general. When the Wii is still selling out from one specific title, a slow Summer doesn't matter too much for that particular system, whereas it has hurt the 360 quite a bit.