MTV's Multiplayer blog investigated further into this, citing that it all comes back to developers getting to know the Blu-ray technology and utilizing its unique characteristics. For multi-platform games like DMC4, the issue is that developers are not optimizing their titles for Blu-ray tech. There are two factors: the disparity between DVD and Blu-ray reading techniques, and the size of Blu-ray discs compared to DVDs. If developers just simply plop down their DVD data onto a Blu-ray disc, essentially, all that extra space on a Blu-ray and the single speed that the data on it is read will cause excessive load times. Think of it this way, if DVD is looking for a needle in a haystack, then Blu-ray is looking for a needle of exact same size in a haystack three times larger.
So what about PS3 exclusives like Hot Shots Golf? A similar concept is involved -- there's too little data on the disc and too much excessive space. Despite this, many other devs have found a work around. One way is to copy data multiple times to fill the entire disc; this allows for data to be read quicker as there are more areas to read from. It's all rather an interesting read, why not check out the entire article over at Multiplayer.