As much as I'd like to agree that it wasn't banished, many Pokedex entries state that it was. I like to consider that since its banishment, it became benevolent. After all, it did stop the destruction of the universe in Pokemon Platinum. And although I hate to be bringing up the anime as a point, but in M10 (pretty sure that was the one), Giratina isn't instantly eradicated on sight by Arceus at the end, leading me to believe that Arceus recognizes that Giratina isn't a malevolent Pokemon. It's too protective to be that.I never thought of Giratina as satan, just a balance keeper of the world opposite of ours, not hell, just a weird LSD trippy version of our world that effects our world.
Also I didn't think Giratina was banish there by Arceus, just a being in charge of the world created when he made our world.
I never even thought of giratina having those hoops, maybe hoopa could be the anti Giratina. Think about normal giratina in our world, hollowed out, minus the head full hoopa woud look vaguely like the inside of giratina from that perspective.
That being said, Hoopa's second form (Unbounded? I forget the name off the top of my head) does look similar to Alternate Forme Giratina. It's typing complements that of Giratina as well. Adding onto this, Hoopa seems to be one of the only two Pokemon seen manipulating dimensions... Aside from Giratina itself.
It's an intriguing possibility, Hoopa having some sort of relation to Giratina. Maybe a failed disciple? The only potential problem is that Hoopa seems to be taking a large part in Gens 6 and the remake of 3... Neither of which correlate with Giratina in Gen 4.
But once again, Arceus has yet to make an appearance, so you never know.