Dreamworld for rides. MOvieworld is ok for rides but not as good as Dreamworld. Seaworld is like Feeb said, more to look at than to do.
If you get a 2 park pass for Dreamworld / White water world, you can take an esky into WWW, chuck it in a locker...then move between the 2 parks. Saves buying food. But, there is nothing to do at WW but water stuff...awesome in summer, not so much in winter!