Twenty-seven-year-old Ronaldo, who now plays for Spanish champions Real Madrid, joined the Red Devils as a teenager in 2003 from Sporting Lisbon.
Despite going on to become a United legend, Neville has admitted that the Portuguese international was not easy to accommodate during his early spell at Old Trafford.
"I will never forget coming back from a game against Charlton some time after Cristiano Ronaldo had signed for Manchester United and thinking to myself: 'Do you know what? I just give up with him,' Neville wrote in his column in the Daily Mail. "He had been flailing around on the ground, he was never in his position and he was unreliable.
"As someone who had played with David Beckham and Ryan Giggs, world-class players who worked up and down and did the ugly part of the game, playing with Cristiano Ronaldo was a constant frustration.
"He would go wandering off to the left, to the right, up the middle. He was inconsistent and he would cost us. I remember him giving the ball away at Chelsea in the Mourinho years and Chelsea scoring. He would win us a match but then we wouldn't see him for the next game."
However, England coach Neville went on to praise the player that Ronaldo has developed into.
"All the premeditated tactical theories I had learned about getting and staying in your shape, and tracking back with your runner, all the things that had been drummed into me, were thrown out over those two years because we had a player who could make up his own rules with the blessing of his teammates," Neville added.
"He changed my thinking. He showed it is possible to accommodate that kind of individual ambition within a team and marry the two together.
"To be able to leave United in his prime and still have his name sung by the fans tells you something."
Ronaldo left United for Madrid in the summer of 2009 for £80m.