Messi received a vote share of 41.60 percent to 23.68 for Ronaldo and 10.91 for Iniesta.
Messi and former French star, UEFA president Michel Platini, had prior to Monday been the only players to win three straight Ballon d'Or awards while Dutch greats Johan Cruyff and Marco Van Basten both won the accolade on three occasions.
Spain's Vicente del Bosque was named coach of the year for 2012, seeing off competition from Real Madrid's Jose Mourinho and former Barcelona coach Josep Guardiola. Messi's success crowned another landmark year for the Argentine who is already the top scorer in La Liga for the ongoing season with 25 goals, having also broken Gerd Mueller's 40-year record for the most goals in a calendar year. He finished 2012 with an astonishing 91 goals in all competitions. But Messi has insisted his scoring records will mean nothing if Barcelona do not go on to take the La Liga title off Real or fail to win the Champions League.
"It is incredible to receive this prize once again and it's impressive it makes it four in a row. I would like to share this with my Barca teammates - particularly with Andres, who is here with me," said the ever unassuming Messi.
"I am proud to be able to train alongside him every day. I am also thinking of my teammates in the Argentina squad," he went on.