What other era's would he not be the best? Pele, Messi, and Maradona are the only players I consider better than CR7 to ever play the game. I just can't see who else would be put over CR7.
Was Maradona really better? From what I've read and clips I've seen...
1) The defending at times was absolutely atrocious on him.
2) He was not consistently at an ATG level (and Evilo brings it up a lot).
Maybe Maradona at his peak was better but depending on what you define as peak you could say a lot of players have had better single tournaments or seasons than many of the all time best. For me what defines an 'all time great' is not how talented they were or how good they were at their peak...but how consistently good they were and how long their primes were. Trophies are not necessities but they help obviously.
You can definitely find more talented players than Ronaldo throughout history but how many can match his consistency and longevity at the top? He's brought trophies, titles and goals galore everywhere he's gone and his work ethic is second to none. I think it's fair to consider him a top 5 player all time.
But again I don't like to compare across generations for many different reasons. Structure, training, video, talent, diet, etc. etc. are all different. Natural progression would suggest that players are constantly getting better, with better training, more instruction, more athletic, better diets, etc. etc. etc.