Ronaldo scored a personal-best 61 goals in just 54 games in all competitions last season, while he became Real Madrid's all-time record scorer last month.
However, Zico feels that Messi should be recognised for inspiring Barcelona's treble triumph in 2014-15, as well as leading Argentina to the final of this year's Copa America.
"I could have chosen Cristiano as well as Neymar," the Selecao icon told Goal. "For me, the three of them are in the top bracket and they can change a match individually.
