Exclusives not only sell more on the 360, but on all segments, increasingly so, and especially on the emerging ones :
Retail X360 vs retail PS3 : Xbox wins (and at a higher price point per exclusive sold )
XBLA vs PSN : Xbox crushingly wins (and this is where Sony truly lags)
Kinect vs Move : Xbox crushingly wins (to be more precise - won - as Move cannot even be considered a competitor)
And this is why gentlemen the common perception that Xbox exclusives sell more than their PS counterpart is... so true