Interesting looking through the production figures of various aircraft.
The top 20 in order of numbers produced includes variants and license builds.
1. Cessna 172. (43,000+)
2. Ilyushin Il-2 Shturmovic. (36,183)
3. Messerschmitt Bf-109. (34,852)
4. Piper Cherokee. (32,778)
5. Cessna 150. (23,949)
6. Cessna 182. (23,237+)
7. Supermarine Spitfire. (20,351)
8. Focke-Wulf Fw-190. (20,051)
9. Piper J-3 Cub. (20,038)
10. Polikarpov Po-2. (20,000)
11. Consolidated B-24 Liberator. (18,482)
12. Antonov An-2. (18,000+)
13. Mikoyan-Gurevich MiG-15. (18,000)
14. Beechcraft Bonanza. (17,000+)
15. Yakovlev Yak-9. (16,769)
16. Douglas DC-3. (16,079)
17. Republic P-47 Thunderbolt. (15,660)
18. North American P-51 Mustang. (15,586)
19. North American T-6 Texan. (15,495)
20. Junkers Ju-88. (15,183)
Those with a '+' sign are supposedly still in production, with the An-2 being built in China under licence as the Y-5.
Not sure how accurate all this is, but it would be fairly close.
Cheers, Willie.