It's a toss up for me between Cr 42 and I-153. Both were still being used as late as 1943, clearly obsolescent by then but not necessarily getting slaughtered on every sortie. I'm not certain about the Gladiator but they may have also been still used in some convoy fights on carriers that late? I'm not sure.
The Finns noted that the I-153 was one of their most feared opponents. Against the Germans the Russians were using them mostly for ground attack, kind of in that HS-123 / OV-10, A-1 Skyraider type role of hypermaneuverable, long loitering, pin-point accurate small CAS and spotting plane. And I think they were pretty effective in that role, carrying rockets and fast-firing machine guns. Obviously quite dangerous to fly around German quality AAA in something that light, but they seemed to get a lot of value from them albeit at great cost, and due to their hypermaneuverability they at least had a chance of survival when bounced (if they saw the fighters coming). They could also be used to attack unescorted bombers of which there were a lot on the Russian front, and an I-153 was more than a match for a Stuka in a dogfight.
CR 42 is still showing up in some numbers in raids in the Med into 1943, also i think relegated to ground support, and of limited effectiveness but still able to kind of hold their own - they took disproportionate losses but not to the extent you might expect, in fact i would estimate they did no worse than say, the Bf 110 or a Hurricane Mk 1. (also still in use quite late) in that Theater. I think the 12.7mm heavy machine guns helped keep these in the game so to speak.
As mentioned before they were duking it out with Gladiators in Africa and the Middle East for much of 1941 with no clear dominant side, seemed like one day the Gladiators would have the best of it. Both Gladiators and Cr-42s could down enemy bombers at least some of the time.
So I guess I would rank them I-153, Cr 42 and then Gladiator. The I-153 probably had the biggest impact because the Russians made so damn many of them (3,000+ on top of the ~3,000 I-15 series), and they used them so aggressively. Many many dead Russian pilots paid the price but they also did some damage to the enemy.
I don't think the F3F was really in the mix (did they see any combat?), though as others mentioned there were some other mid-war biplanes which were still fighting in the Spanish Civil War, in Manchuria, and in the early years of WW2 proper. These included the afore mentioned Cr-32, He 51, I-15 and
Gloster Gauntlet, also the
Hawker Fury,
Britsol Bulldog, and the rather elegant Czech
Avia B-534.
If you include parasol winged planes you also have the Pzl P-11 / P-24 (surprisingly good and was the basis for the excellent IAR-80) and the Ikarus IK-2.
Only the I-153, Cr 42, and Gladiator Gladiator had the speed - roughly 250-280 mph, which allowed them to really compete in even early WW2. I think that is the main difference. Somewhat heavier armament and things like a little bit of pilot armor also helped. The Cr 32, B-534, P-11 and Gloster Gauntlet were kind of in a second tier at around 220 -250 mph. Most of the other interwar biplane fighters could barely make 200 mph and therefore couldn't even catch the slower bombers, which made them almost useless.
S