I would have to say the Stuka was the most well known in Europe as the Lightning war swept the continent. Thos dive sirens were terror weapons. But since that's not a fighter, the 109 was built in greater numbers than any other plane in the war.
Spitfire for the Brits.
Mustang for the Yanks.
Zeke for Japan.
Overall....probably the 109 because, if you think about it, every country in the war faced it at some point.