The Avia 534 should be mentioned as a contender, although the CR 42 still would have the edge.
It was strange that the Italians continued to develop the biplane at so late a date. It would be like Ford Motor Co. building the Pinto in 2006...the ultimate Pinto, no doubt, but why?
From the late 30s era, you also would have to take a look at the Grumman F3F. True, it did not participate in WW2. However, the Al Williams Gulfhawk version had a top speed of 290 mph (no armor or armament, of course).