Everyone (not really) found the Americas before Columbus. His was just a major milestone in history when the ‘discovery’ was used on a mass scale.
Agreed. One could argue that Columbus's 1492 voyage marked the beginning of sustained nation-state sponsored discovery and exploitation of the results of those discoveries. Anything before that (the Vikings, the Polynesians, the Basque fishing fleets on the Grand Banks, the Chinese, if that happened) lacked long lasting settlement and associated cultural impact on peoples in both the Americas and Eurasia.
I think Columbus's voyages also have importance because they are fairly bright line marker for the ascendancy of Europe on the world stage.