Henry guided the All Blacks to victory in 2011 at home while his assistant Steve Hansen repeated the win in England four years later.
Henry, however, said he was more confident of New Zealand's success in 2015 than the upcoming tournament and added that several teams are capable of lifting the Webb Ellis trophy in Yokohama on Nov. 2.
"I think our buildup into the World Cup was very positive and we won just about everything," Henry told radio station Newstalk ZB on Saturday about the All Blacks' form ahead of the 2015 tournament.
"In the last couple years, we haven't looked as (good)."
After a superb 2016 Rugby Championship season when they took their game to a new level, the All Blacks lost to Ireland for the first time in Chicago, then drew the test series against the British and Irish Lions in 2017.
Last year they lost to South Africa in Wellington, sneaked to a lucky one-point victory over England and lost again to Ireland in Dublin.
"I went on the tour last year to England and Ireland when they played in those two tests in October or November, and they looked fat," Henry said.
"And they didn't play particularly well against the Lions (so) I don't think they've had the same buildup as they've had for 2015."
Henry said the 2015 side had several all-time great All Blacks players and the retirement of the majority of them have contributed to the dip.
"When Richie McCaw and Daniel Carter and Conrad Smith and ... Keven Mealamu all move out together there's probably going to be a little bit of a drop," Henry said.
"So that may be the case."
Despite his concerns about the progress of the All Blacks, and the challenge from Six Nations teams like champions Wales, England and Ireland, Henry was confident Hansen would have a side capable of winning the tournament.
"I think it's going to be a really interesting Rugby World Cup," he said.
"I think if the All Blacks play to the peak of their powers they will do the business but that's the question - 'can they get up there again and do the job?'
"My gut tells me yes but I think it's going to be more competitive than last time."
(Reporting by Greg Stutchbury; Editing by Sudipto Ganguly)
