erm this is how i got dialga and palkia.....a bit after i finish the elite four and cynthia i talked to lucas who was in sandgem town he told me this random crap then go to celestic town and talk to the elder in the wide house and then she tells you more crap that shes seen them and stuff.then go to mt coronet the orebugh city way and there should be this cave to the right of you after you scale the first wall.go inside and use waterfall to go to another cave and there will be 2 pokeballs and a stone get the 2 pokeballs and there should be an item on the rock.after that exit out and make your way to the spear pillar.when you are at the spear pillar there should be this blue tear in the thing which looks like you can jump into some sort of dimension(i thought that at first)and it will be dialga.its best to save your game before you battle these two just in case you kill them or get defeated or run out of pokeballs.after you defeat or catch dialga go back and go in this time there will be a pink tear again save and battle.i recommend to get alot of ultra balls or master balls if you have a R4.and as Sparr64686 said they are level 70.

you guys both left something out:
you have to talk tot the elders before you can catch Dialga and palkia

i said that >_> i said "then go to celestic town and talk to the elder in the wide house"

o srry i guess i didnt have time to read the thing
buut the guy who posted the cheat left it out

I'd say use a luxary ball if you don't have any master balls.