Brazil's Ronaldo -- Messi Is the Greatest Player Alive ... Sorry Cristiano

Brazil soccer legend Ronaldo -- considered one of the greatest players EVER -- has touched down in Beverly Hills ... and last night he weighed in on the great soccer debate -- Lionel Messi vs. Cristiano Ronaldo.

The argument has been raging for years -- with people claiming each superstar has a valid claim to be called "The Greatest." In fact, some people have said they're the two best players of all time.

So, when Ronaldo was leaving Madeo ... where he had the veal milanese by the way ... we had to ask if he thought Messi deserved to be called #1.

Bonus -- wanna see why Ronaldo's considered a god? Check out the clip below ...