if you have pokemon emerald trade your strongest pokemon on emerald over to sapphire because it will be easier to beat the elite fourth pokemon i used were:
lv.76=rayquaza
moves=Fly,outrage,fire blast,dragon claw
lv.60=latias
moves=hyper beam,psychic,thunder,fly
lv.71=blaziken
moves=blaze kick,fire puch,overheat,fire blast
lv.60=latios
moves=fly,psychic,luster purge,dragon breath
lv.60=groudon
moves=fire blast,rest,fissure,solarbeam
lv.61=swapert
moves=earthquake,blizzard,muddy water,sheer cold