from objective side I would sa Focke-Wulf was best sigle engine plane of ww2.
As a French,let me be free to recal Dewoitine D.520, in 1940 on a pair of Spitfire and Me-109,of course our defeat stopped further improvements.
For sharp-eyed of you,with some skill in design recognition,D.520 design(cockpit position,proportions) is similar to famous later war Vought F4U Corsair,and some experts think it was design influence.