Manchester United legend Gary Neville says Cristiano Ronaldo is the "greatest football player that has ever lived".

The 36-year-old scored twice on his second debut for United last Saturday, as Ole Gunnar Solskjaer's ran out 4-1 winners against Newcastle United.

"I've always ignored the Ronaldo and Messi question, it's a bit of a fantasy and both need to be enjoyed," the former United right-back told Sky Sports' Monday Night Football.

"I was asked this morning by a gentleman who was driving me in: If you could pick any player in history to come off the bench and win you a game, who would it be?

"It would absolutely be Cristiano Ronaldo. I do think he's the greatest football player that has ever lived. That is not a bias.

"Messi is a ridiculous player who's scored an obscene amount of goals. It's incredibly similar (on the stats) apart from the wrong-footed goals, the headers, and the penalties.

"That takes me to a point whereby he's more complete in terms of the most important part of the game. What tips me is the international record, the most goals of all-time, and the five Champions Leagues with worse teams than Messi's."

However, Neville's fellow Sky analyst and Liverpool legend Jamie Carragher disagreed.

"Ronaldo is not the greatest player of all time. I'm going to say it's his mate here (Messi)," Carragher said.

"It doesn't matter how a ball goes in the net, Messi has more goals than Ronaldo. Messi is also a playmaker, he can run a game, Ronaldo can't do that.

"Talk about who you want coming off the bench, Messi has scored more goals coming off the bench, so that's a ridiculous thing you've said there.

"Ronaldo does things other players can do, Messi does things we've never seen before. In terms of the goalscoring that's not right.

"There's been a lot of fanfare about Ronaldo from ex-players, I just think you've just got carried away."