The debate over who is the better player - Lionel Messi or Cristiano Ronaldo, will never die down, and according to Sir Alex Ferguson, there is nothing to compare between the two, because the deadly duo are equally great.

The Manchester United manager is of course well versed with the talents of Ronaldo having seen him blossom into the world's best player at Old Trafford before making his dream move to Real Madrid.

While Messi on the other hand has been breaking one record after another with the latest being the most goals scored in a calendar year, which was previously held by Gerd Muller who netted 85 times in 1972.

Messi is currently on an astonishing 90 for the year, with one more game in the La Liga to go before the year ends.

Both players, along with Barcelona playmaker Andres Iniesta, have been shortlisted for the FIFA Ballon d'Or, with Messi the overwhelming favorite to win the award for a fourth time.

 "There is nothing between the two of them, they are both the best players in the world," Ferguson was quoted as saying in The Sun.

"There will always be great players. You can go back to the 60s with Alfredo Di Stefano, Ferenc Puskas and Eusebio. Going into the 70s you had Johan Cruyff and Franz Beckenbauer and then in the 80s Marco van Basten.

"I think what we are seeing at the moment is that Messi is an exceptional player from this decade, along with Cristiano.

"I don't think the rivalry against each other bothers them. I think they have their own personal pride in terms of wanting to be the best and I certainly know that about Cristiano because he played here at United for six years."

Ferguson could yet be set for a reunion with Ronaldo, with United having a chance of being drawn with Real Madrid in the Champions League, when the draw for the last-16 takes place in Nyon Thursday.