Funny thing is if you dig and do some research, the old titles that are both available on Blue Ray and DVD, sells a lot more in Blue Ray relatively compared to the top 20 titles... Granted there is a huge number of title only available in DVD...
Probably because at this point there is little interest for someone to buy the DVD of "300" or "Batman Begins" but it seems some people that got into Blue Ray recently are rebuying some of their old title in that format...
The week before Iron Man released 300 had a 30% Blue Ray market share in numbers ( for every 2 DVD sold, 1 Blue Ray was sold).