In my view, there's only 5 continents on the planet (Eurasia, North America, South America, Africa, and Antarctica). Anyway, back on track...
These are my guesses:
Vikings - Founded Russia, shaped modern Scandinavia, mingled with Britain
Babylonians - Rose to power. Twice. In two very different eras. And conquered the Ferticle Crescent. Both times. Also made significant contributions to science.
Portuguese - Seriously competed with Spain for control of the New World and several other areas
Byzantines - Ruled parts of the Middle East, the eastern Mediterranean, and southeast Asia for a thousand years.
Ottomans - Conquered the Byzantines and knocked on the doorstep of Europe.
Sumerians - Founded civilization and made significant contributions to science, math, engineering, etc.
The Mayans, Ethiopians, Dutch, Austrians, Koreans, Carthaginians, Celts, Hebrews, and Siam all got consideration on my part, but I think these are the most deserving.