Neville did not do too badly during his own playing days, collecting eight league titles and a Champions League winners' medal in a substantial trophy haul before quitting the game in the middle of last season, but he will always be overshadowed by Giggs, leader of that famed Class of 92 which spawned so many medal collectors.
Should United go on to lift the Premier League title this term, it would be Giggs's 13th, and Neville said: "Ryan is 38 years old, and he will contribute at the age of 42 if he wants to, the way his body is right now, the way his football is and the quality he still has."
He added: "Will we ever see his like again? No, no way. Ryan Giggs will go down as the most successful British footballer of all time and I cannot see anyone ever overtaking him. He's on the brink of his 13th league title, after all.
"When we were younger, we often heard about Alan Hansen's amazing eight championships with Liverpool. But what we are witnessing at the moment is greatness before our very eyes.
"Ryan is unique, he has surpassed all records in terms of domestic titles and he has incredible desire, quality and spirit. He's just fantastic to watch.
"You give up asking how long he could go on for. Why bother? When you see his quality and what a contribution he makes to the team why would he even think about it?"
Neville was speaking as part of a series of interviews carried out on behalf of the Premier League leading up to the end of its 20th season.
Giggs is the only player left who has featured in them all, which in itself would make him a contender to be number one, and Neville continued: "The best player in the history of the Premier League? It's got to be Ryan Giggs, no question at all.
"He has constantly adapted his game. He went from being a flying winger in the early days to someone who could play off the front, to a central midfielder, and even to left-back if required. He can play anywhere and that's what really great players do: they adapt."