Yes, Wilt was better than Kareem Abdul-Jabbar. When they played against each other in early '70s, it must be remembered that Abdul-Jabbar was ten years younger than Wilt. If they were the same age when they played each other, I think the results would have been startling.
Wilt didn't have the sky hook, but could score like Kareem when in his prime (and when Wilt's teams depended upon him for points), and Wilt's rebounding was always unsurpassed. Chamberlain led the NBA in rebounding during his final season as a player, and his per game average is more than double Abdul-Jabbar's. I believe them both to be outstanding passers and defenders.
This takes nothing away from Kareem, whom I believe to be one of the five best players (not just centers) in the history of basketball. I simply believe Chamberlain was the very best.