This post is now open to discussion. Enjoy.
Gioachino Greco vs Ruy Lopez de Segura

The "computer age" for chess didn't begin until the 1990s.
This is an age old question.

They were both patzers.

They were both patzers.
That's one possible uneducated opinion.

Actually they were great players, and I suppose Greco would have defeated López, since Polerio and Boi did it before.

It's true, and well accepted that Gioachino Greco and Ruy Lopez de Segura were the two greatest players before the computer age.
I think that no experienced player could agree with you, because Greco and Ruy Lopez were probably the strongest in their time, but nothing compared to Fischer, Capablanca, Alekhine, Lasker, Botvinnik, Nimzowitsch, Najdorf, Steinitz, Rubinstein and the list goes on...
Honestly I wonder what are your sources.
If you want to get an idea, search "the greatest chess players of all time" on internet.
Personally I believe that Fischer was the greatest before computers, but we can't be sure about that. It can also depend on what we mean by "greatest".

It's true, and well accepted that Gioachino Greco and Ruy Lopez de Segura were the two greatest players before the computer age.
I think that no experienced player could agree with you, because Greco and Ruy Lopez were probably the strongest in their time, but nothing compared to Fischer, Capablanca, Alekhine, Lasker, Botvinnik, Nimzowitsch, Najdorf, Steinitz, Rubinstein and the list goes on...
Honestly I wonder what are your sources.
If you want to get an idea, search "the greatest chess players of all time" on internet.
Personally I believe that Fischer was the greatest before computers, but we can't be sure about that. It can also depend on what we mean by "greatest".
What are my sources? What are your sources? What are sources anyway?

If I recall correctly, the rules of chess had been changed in the 1470s, greatly changing the way that the game was played. The Queen went from being the weakest piece on the board to being the most powerful piece, for example.
Greco and Ruy Lopez lived in what might be termed a golden age of chess. They were, in a sense, pioneers.
They didn't need to be particularly strong players... and they weren't. They were explorers in a wilderness.

I would say Greco has a slight edge, though the game would undoubtedly be drawn. These two played pretty much perfect chess, envied by the likes of engines. A better question is who would win, Ruy Lopez de Segura and Gioachino Greco, or a team of Kasparov, Fischer, Carlsen, Stockfish, Komodo, Morphy, Capablanca, Alekhine, Tal, Lasker, Aronian, Giri, Nakamura, MVL, and Kramnik. I give a slight edge to Lopez and Greco, because of their incredible skill, but IDK.
This would be interesting.
It would also be interesting to have seen Greco, blindfolded playing a simul vs Stockfish, Rybka, and Komodo
If we set up a poll, with the question "Who was the greatest chess player before the computer age", and were able to survey all the greatest chess players who have ever lived, we would not be able to get a consensus. This is because 2 options would be chosen at the same rate.
It's true, and well accepted that Gioachino Greco and Ruy Lopez de Segura were the two greatest players before the computer age. But who would prevail in a match if they ever got to play each other. I know, it's hard to imagine, but if you were to choose, who would you favour?