Sony have to Support both the PSP and PS3 whereas Microsoft only has to support a single console - Sony requires a large amount of studios whereas Microsoft doesn't need as many. Sony also has a larger Third party support base than Microsoft too - It shows that Mega titles very rarely turn into a large increase hardware sales
<a href="http://eu.playstation.com/psn/profile/cleaner475/"><img src="http://mypsn.eu.playstation.com/psn/profile/cleaner475.png" border="0" /></a>