hey there-- that's sick as in "That was some sick 'computer animation' in Pixar's newest production..."
or, "Steve Vai, Yngwie Malmsteen, and Jimi Page are all sick guitarists in their own right!.."
probably comes from ... "man, you make me sick!" when li'l Billy was shocked at li'l Johnny's skill, prowess, and natural talent-- knowing that he is unable to produce such an outstanding work as Johnny's, Billy is made 'sick', while Johnny earns the implied title as the 'sick artist'.