Many ways to compare blu-ray to DVD
Total DVD vs Total blu-ray is also unfair since there are only around 500 titles currently on blu-ray of course many titles are not selling well on blu-ray they are not even available !.

Would be interesting to see how an older title re-release like 2001 originally shot in 70mm film (i just ordered a blu-ray) or new release like BBC's Planet earth which was filmed in 1080p for HD media compare. And how blu re-releases do like the possible upcomming "Dark City" blu-ray.

I think the truith is somewhere in between but one thing is for sure blu-ray is surging upwards very fast.
A projected 30M players in circulation by end of 2008 should result in over 10% of the total optical media market being blu-ray by the end of this year.
The current ~10%:90% (Blu:DVD) will rise to ~20%:80% by end of 2008 and with ~600 current and probably over 1000 titles by end2008 it could make 10% of total market and 20% for new release movies.

This article
http://www.cdfreaks.com/news/Blu-ray-sales-hit-record-in-Japan.html
It Reads Blu-ray is now 18.2% of optical media market in Japan.

 How is it unfair to compare them all when you are measureing the amount of market share Blu-ray has captured?

Market Share = Amount of products sold vs your opponents.  Coke has more kinda of Soda then RC cola.  Yet you don't isolate Coke vs RC cola to test marketshare.

If you want to see how well blu-ray would do if all movies were in blue-ray you take those 500 titles and compare them to the same 500 DVD titles. 

Which they don't do because it paints it in a more negative light because Blu-ray sales are likely a LOT more frontloaded. 

Well yeah. Blu-ray was out in Japan before anyone over here even knew what it was. Blu-ray was in Japan before there were even blu-ray discs.

They used to use Blu-ray cartridges.

They hit the market in Japan in like... 2003. It's been out for 5 years over there.

The cartridges kicked ass. I kinda wish they would of kept that format look.

Seriously google image search it. It looked kickass.

 I remember those things, they had a bucnh of articles about them in PSM back in the early days of the PS2.

The actual movie format for blu-ray is far newer than the older physical media standard. If you actually read the article>
http://www.cdfreaks.com/news/Blu-ray-sales-hit-record-in-Japan.html
It mentions that the majority of the increase to over 18% in japan was in the last 6 months - It jumped from under 2% to over 18% in under 6 months !
The data Cartridges were for DATA storage not Movie distribuition. Cartridges cost more to make and are bulky so you cant use a cd folder.
Blu-ray as we know it is only a few years old and required the developent of a scratch guard coating.

Just went up to 8% this last week. Link will come soon.

Impressive ... the % will probably only grow in the favor of the BD during holidays season :)

 comparing 500 blu-ray movies to 500 DVDs still isnt' fair for DVD though.  Those 500 blu-ray titles were picked to be released by the companies because they thought there was a market for it on blu-ray.  many thousands of DVD has not made the change to blu-ray because the market simply isn't there for it.  Comparing 500 DVDs to 500 Blu-rays only shows the market for those 500 movies, or those type of movies.  

The real reason why blu-ray has not taken of is because people dont know what it is, sony doesnt advertise it.