In this day and age, exclusive third-party titles can no longer be counted on to push a console, so thus the onus falls on the console manufacturers. While inherently attached to one console by their nature, first-party titles can still sell significant copies and "rally the base" of a particular platform. A system without good first-party software usually has a hard time finding its audience, making it all the more crucial.
2006: While many projects were promised to be in development for the PS3, there was very little to show from Sony at the system's launch. Resistance: Fall of Man was a notable bright spot, with Untold Legends: Dark Kingdom not having much impact and Genji: Days of the Blade doing little more than inspiring mocking tributes of "Giant Enemy Crab." When Motorstorm was delayed until March, the selection of quality first -party titles on the PS3 was slim for quite a while.
2009: It's taken a while for things to spin up, but development seeds planted long ago are finally starting to sprout for Sony Computer Entertainment. Already this year, Killzone 2 and inFamous launched beginning what the company called a "relentless" release schedule of quality software. Looking at the release schedule heading into 2010, it's difficult to disagree: Uncharted 2: Among Thieves, Gran Turismo 5, MAG, Heavy Rain, God of War III, The Last Guardian and more are all on the slate. The bottom line is great software is what drives this industry, and PS3's first-party efforts will likely be the platform's greatest strength going forward.