SingStar for the PS3 was released in December 2007 (in Europe). Was meant to be the console's killer app amongst those who didn't fancy Heavenly Sword, but it hasn't really worked out that way.
That's mostly because PS2 owners who play SingStar still play SingStar on the PS2. Sony keep releasing PS2 versions of the game, so PS2 owners don't need to upgrade. Simple.
A smaller, though not insignificant reason is that the game, despite being for the all-singing, all-dancing PlayStation 3, shipped with the same rugged, ageing USB mics the PS2 version did. This despite promises the game would ship with fancy new wireless ones.
With Microsoft's Lips - which, for all the game's flaws, has excellent wireless mics - perhaps serving as a kick in the butt, Sony are now finally acting on the whole wireless mics thing.