Pele>>Maradona>Messi>Ronaldo>Cristiano
In my opinion you can't compare players from the 70's vs 90's+ imagining for example Messi playing in 1970 and saying he would be a God. Or Pele playing nowadays and saying he would suck completely.
I think the "best" way to do this is watching how was Pele/Maradona's performance compared to other players from the same time with the help of some numbers and analyzing how much better are Messi and Cristiano comparing to current players.
I dont know if you understand what I'm saying

PS: For me (and for several instituitions like IFFHS, FIFA, L'equipe, etc) , winning 3 WC, scoring over 1200 (including non official matches) and winning all this prizes are more than enough to be considered the nÂș 1 football player in the world...