Barcelona playmaker Messi is on course to win the award for a record fourth time.
The 25-year-old has scooped the FIFA prize for the past two years and also picked up the Ballon d'Or in 2009 before the prize was combined with the FIFA World Player of the Year title.
The Argentine has already netted 82 goals since January and will match Gerd Muller's record for goals in a calendar year for club and country if he scores three more.
He helped Barcelona to their 2012 Copa del Rey triumph as well as playing a key part in Argentina topping their 2014 World Cup qualifying group.
Ronaldo has also enjoyed a fantastic year as part of Real Madrid's La Liga-winning side and reaching the semi-finals of the European Championships with Portugal.
The forward previously picked up the award in 2008 but finished as runner-up behind Messi in 2009 and 2011.
Barcelona midfielder Iniesta, who finished second in the voting to Messi in 2010, helped Spain to defend their European title this year.