Did you notice how many of your examples were famous not because
of their use of the Spanish language, but rather irrespective
of their spoken language?
Gaudi was known for his Architecture, Dali, Goya and Sorolla for their paintings, Paco de Lucia for his guitar mastery. They would probably have been as successful regardless what language they spoke. Pizarro was unschooled and illiterate. He is known mostly for his greed in plundering Peru, and perhaps the fact that he did NOT master Spanish was an asset when conquering a people who only spoke native languages at the time.
Cervantes is among the few that anyone cites when the subject of Spanish literature is raised. But for instance there were MANY landmarks of literature in Italian already when Cervantes rolled into town, and many after; for instance Petrarch, Boccaccio, Dante (Divine Comedy), Machiavelli... and likewise with French. Despite the fact that much more of the world speaks Spanish than French, there are far more Nobel Prizes per capita in French than in Spanish.
I've read Cervantes in the original Spanish and honestly I'm not impressed. It's a wacky tale and has a place along with such works as Alice in Wonderland, but it's sad that it's the best that anyone can come up with when trying to legitimatize Spanish literature.