Considering that when speaking in percentages, Blue Dragon had a large impact on 360 sales, that's a pretty vague statement. Here's the charts... I'm sure you can figure out when Blue Dragon launched for the 360.
Before Blue Dragon, the 360 was moving about 1k a week in Japan. It was completely dead in the water. Now it's merely on life support
I have seriously never seen a system chart like that. I'm aware we're talking percentages -- that in terms of consoles sold, I'm sure some systems have seen more dramatic upswings simply because they were dealing in the millions or even tens of millions instead of in the hundred thousands -- but I highly doubt that any single game has ever produced a more dramatic and visible upswing in system sales. Seriously, ever, for any market. Can anyone find a graph on the site that shows a more dramatic effect than that?