I've always rated Movie World the lowest, but they've got some new rides that are pretty good. Dreamworld has the best rides (and also lots of kangaroos you can pat, but basically every zoo or wildlife park in Australia has those), Wet'n'Wild is the best water park, and Seaworld has a tank full of adorable stingrays that come right up to you for pats :3
I haven't been to White Water World. You can get cheaper group deals for Dreamworld and White Water World, or for Seaworld, Movie World and Wet'n'Wild.