ARCEUS
zapdos
No. Regigigas can cream Palkia! However, Palkia's speed is faster. It could attack first.
Dialga, Giratina, Heatran, Mespirit, Uxie, Azelf, Regigigas, Rotom, Cresselia,
Rayquaza is stronger because his moves are stronger. Giratina only has one move that is power over 100. That's Shadow Force. Rayquaza has 2 moves that are power over 100.
Giratina is stronger.
Regigigas
It's the same movie Shaymen and Giratina are in.
Regigigas. Check out serebii.net's Pokedex
Dialga, Palkia Giratina, Regigigas, Lunacress
ARCEUS
Mesprit, Azelf, Uxie, palkia, Giratina, Heatran, Cresselia, Regigigas, rotom(debated).
The legendaries in Pokemon pearl are Palkia, Regigigas, Giratina, Cresselia and Heatran.
Dialga.
zapdos
You can get Dialga, Uxie, Mesprit, Azelf, Darkrai, Arceus, Shaymin, Cresselia, Regigigas. You can also get Manaphy. You can also get Giratina Dancer_Pokemoner Neojoejoe
only if you have a level 100 regigigas and a level 100 shaymin