I think youd have to do it by generation, as there are some significant changes by generation as well as intent (when you get to the later years there was more of a focus on handling handling vs the earlier focus on comfort handling).
In addition, its important to consider that skidpad Gs do not equal handling. Ive driven race cars that would do an epic skidpad number but are so ill handling in transition/under braking/whatever, that they are virtually undriveable.
I have the most experience with 1st gen w-bodies, and my vote there would be for the FE3 level Grand Prix coupe with the 245 wide tires. Though I suspect/wonder if the 1990 olds international with FE3 and the quad 4 would be the ultimate iteration for handling. Ive never driven one (almost nobody has) so I cant say definitively, hence my mention above of the 245 tire equipped GP.
For gen 1.5, Im not sure.
For the last generation, its most likely the 2008 GP GXP. The fact they fitted reverse stagger tires (and engineered the suspension to utilize this setup) tells me someone understood how to make an FWD car handle.