As things stand:
Tier 0: Pelé, Maradona, Messi ▲
Tier ½: Beckenbauer, Ronaldo ▲, Di Stéfano
Tier 1: Cruyff, Platini, Fenômeno, Puskás
Followed by the likes of Eusébio, Best, Müller, Maldini, Mané Garrincha, Xavi, Baresi, Matthäus and co. in slightly broader tiers.
▲ signifies that Ronaldo and Messi are the only variables on that list - and the only direction their profile could go in the future is up — with the current position on the tier-list being the minimum bar for what they've achieved, thus far.
The reason why I hesitate to put him in Tier 0 is that Cristiano just doesn't really have the air of magic of those three, and he hasn't had that since the early parts of his Madrid career. That isn't some damning criticism because he's pretty freaking imperious in his own right and terrorizes defenses like few others, but there's no getting around the argument that he doesn't quite share their ability to make an impact from seemingly anywhere on the pitch and carry his team outside of his goals with greatest-of-all-time caliber play-making and passing nous and technical flair. In fact, you'd hesitate to put him above Cruyff, Platini and co. as regards his general play as well. In terms of pure wow factor, he's a bit like the Jerome Bettis to their Barry Sanders - which is probably the most consistent criticism of him as a player as regards his historic profile, and he stands out as a glitch in the matrix in the pantheon of greats — almost like Müller on crack.
But his goal contributions are too overwhelming to sweep under the rug at this point, and you'd have to be a bit tone-deaf have to not rank him as probably the greatest European player with Kaizer Beckenbauer. Equally ridiculous is the consistency of performance in terms of tangible impact — one that is matched by only Pelé and Messi, and Puskás - who's oftentimes marginalized in a lot of discussions - even though he started performing at an excellent level for Kispest at a young age, then Honvéd — followed by 4 Piccichi titles and 3 European Cup titles for Madrid after joining the club at age 31, and that's aside from his record for Hungary, and European scorers - which Ronaldo will likely break in the immediate future. On a general note, it's pretty amazing that Cristiano's managed to shamelessly insert himself in the these discussions because for the longest time, it seemed like he would definitely play second fiddle to Messi and Barcelona's dominance across the era and languish on the edge of Top 10 of all time. Speaks volumes about his relentless drive to win, sheer strength of will, and superhuman focus. He's probably THE greatest of all time in that department with Pelé for football, and the likes of Jordan and Brady for sports at large.