E3 2008 in general showed how insignificant the event was becoming. I remember being so let down that year. I think Sony might have had the best showing but I can't remember. I do remember Microsoft's big reveal was that Final Fantasy XIII was also coming to Xbox 360. By then we had hearing so much about Final Fantasy XIII to the point where the announcement was almost meaningless. As for Nintendo, yeah, E3 2008 showed everyone that E3 performances are not reflective on sales at all. Another great example of this is Microsoft in 2010. Everybody hated their show that year, but Kinect made them a lot of money.
Yeah Kinect adventures sold like 20m (I think it was the best selling game that year) and it was the most notorious showing in E3 by miles mean while 2010 was one of Nintendo's best showings and sales that year slowed down, no wonder companies began cutting back on the event.