[AbRASiON]

Now would you prefer them encoded? H.264 was certainly the best option at the time. Would you have preferred mpeg2 at double the bitrate or half the quality? Or maybe no compression and shuffle half a dozen discs to play 1 movie?

I am sure the basic requirements for bluray compatibility are easy to find. Start at wikipedia.

Obviously h.264 which is the best option, however in the past 3 or 4 years I've seen many posts about all the different and subtle features buried in advanced h.264 encoding. The anime guys are generally the ones to take advantage of all the best features.
Just throwing bitrate at a problem won't always solve it. I'm probably being paranoid but it would be nice to know that the blu rays are at least generally, always encoded with the best colour depth possible for example. (is it 10:10:10 or some such?)