http://skepticalsports.com/?p=112 is the first article of a series of posts on Rodman. Read it; it's really interesting stuff.
Let's put it that way: Rodman grabbed the highest % of rebounds anyone ever grabbed, and did so over the course of five seasons. He did average less RPG than Wilt or Bill, but their games were played at a faster pace, and with lower shooting % than in the 90es. Usually, players have to give up offensive rebounding when trying to get defensive rebounds, and vice versa. Rodman is basically the only exception to this: when he grabbed more defensive rebounds, he also grabbed more offensive rebounds. Kevin Garnetts career rebounding %age is actually lower than Rodmans career
offensive rebounding %age.