"It's like cars. Some cars are better than others, that's why they're more expensive. It's the same with players. But this is only my opinion."
Ronaldo has collected a number of accolades for his 42-goal season but the 23-year-old still only rated last year's showing as nine out of ten. He insists he has more to give but the frustrations of injury at the start of the current campaign hampered his chances of a repeat performance.
"How do I rate last season? I can't say 10 out of 10, so nine. I can improve all the time. Ten is the maximum and I haven't reached the maximum yet, so I'd give myself nine.
"My challenge is always to be better and better.
"This season I'd give myself eight out of 10. Some circumstances have gone against me, like at the start of the season when I was injured, but I don't want to think about that.
"I'll try to be as good as I was last season, but it's hard."
Ronaldo has been named European and World Player of the Year in recent weeks, but he resolutely states that succeeding on an individual level is not his priority and his ambition remains winning trophies with United and Portugal.
There is also no room for complacency in his world as he says relaxing can lead to being left empty handed.
"Being the World Player of the Year is a great feeling, but it doesn't change anything in my personality, my character, my ambition. I'm still the same" he said. "I want to win games, help United to win trophies. This is my ambition.
"Me scoring is not important, as long as the team wins. If that happens, I win too. I know if I keep working hard and doing the right things.
"If you relax it's not good. Maybe sometimes you relax automatically, but I don't want that. In my head, I know and I am always thinking, 'Cristiano you have won nothing' and I want to carry on like that."
Since joining United in 2003 he has won two League titles, the FA Cup, the League Cup, two Community Shields, the European Cup and the Fifa Club World Cup. And as for the future Ronaldo is not short on his list of 'things to win'.
"I have the Champions League award – a replica – but I want another one," he said. "The feeling of winning that trophy was great. I want to win it again.
"My dream is also to win the World Cup and the Euros. I want to win more things for the club. The cups, the Premier League, Ballon D'Or, World Player of the Year, I want to win them all again.
"Winning is the most important thing. When you win, everything is good. Winning, scoring and beating defenders – that's the order in which I like it.'