Doubt it was quicker adopted than DVD though. DVD offered a massive benefits over the format before (resolution, sound, convenience etc) so was quickly adaopted. There also was no format war and consumers were keen to buy. By comparisson, Blu Ray doesn't offer a huge leap over DVD - with slight resolutiion and sound - and with the format, it was pretty slow to get buy in.
I'm guessing maybe they mean by units sold (BR vs DVD players) - and in that case they're taking into account the almost 30 million PS3 out there. Of those, you'll probably find 29,800,000 bought it for games as a primary function.
http://en.wikipedia.org/wiki/Blu-ray_Disc
According to Adams Media Research, high-definition software sales were slower in the first two years than standard DVD software sales.[46] 16.3 million standard DVD software units were sold in the first two years (1997–98) compared to 8.3 million high-definition software units (2006–07).[46][47] One reason given for this difference was the smaller marketplace (26.5 million HDTVs in 2007 compared to 100 million SDTVs in 1998).[
And since HD DVD was around in that period, we can take off those sales from the 8 mlillion odd HD ...
I wonder if the average consumer can really spot the difference, or if they can is it really enough to convince them to change. As you have stated the benefits of DVD over VHS were astronomical, to many people this may still be just another optical media.