The duo played together on the right flank for Sir Alex Ferguson's side for a time and the former England international revealed that he had doubts over whether the winger could truly adapt to the English game.
He was happy to be proved wrong, however, when the 27-year-old returned from World Cup 2006 and matured quickly, with Neville describing his form as "on another planet" as he won the Ballon d'Or.
|MANCHESTER UNITED LATEST
|8/1||Cristiano Ronaldo is 8/1 with William Hill to score a hat-trick against Manchester City for Real Madrid
"He has helped to redefine the game by creating a new breed of flexible forward.
"He was always fascinated with becoming the best player in the world. You would always say individual honours aren't important but, to Ronaldo, they were.
"He showed it is possible to accommodate that kind of individual ambition within a team and marry the two together."
While Ronaldo lit up the Premier League for the Red Devils - scoring 91 goals in all competitions between 2006 and 2009 - Neville suggested that the forward left him exasperated at times.
"I will never forget coming back from a game against Charlton some time after [he] had signed for Manchester United and thinking to myself: 'Do you know what? I just give up with him'," he remarked.
However, Sir Alex Ferguson persevered with the forward and Neville recalls that he returned from World Cup 2006 with a point to prove, noting: "What ensued for the next two years was astonishing.
"I can't believe anyone has ever seen anything as extraordinary in the Premier League.
|"Perhaps Thierry Henry in his prime came closest but for two years this was a player on another planet, the best in the world"
- Gary Neville on Cristiano Ronaldo
"I know we have had Thierry Henry, Eric Cantona and Gianfranco Zola - and perhaps Henry in his prime came closest - but for two years this was a player on another planet, the best in the world.
"For anyone who appreciates football, it will be a privilege to watch one of the great players of all time."