Jokes aside, the Roman legions were so insanely good at fighting and military logistics that the defeats they suffered are still remembered today - precisely because they were so few.

After the Punic wars, the only peer competitor left was the Parthians/Persians. Everyone else got a few lucky hits at best, if they could exploit some major mistake (full respect to Arminius in the Teutoburg Forest, that is how it is done, but not every commander was as heedless as Varus).