Ronaldo helped Real Madrid to the Champions League and La Liga double last season as Los Blancos became the first team to retain the former and ended a five-year wait for the domestic title too.
Messi is expected to be the closest challenger to Ronaldo once again, with the pair having won the last nine Ballon d'Or trophies between them, but Pique acknowledged that the Madrid man has the edge this year.
"Cristiano Ronaldo has won the Champions League and La Liga, so he is a favourite," Pique told Qatari television.
"Lionel Messi is still considered the best player in history, though, and then there are other options."
Should Ronaldo win this year's award then he would draw level with Messi on five Ballons d'Or each.