I rock.
Diamond-Giratina was really easy, I caught it on my first try with my fourth Great Ball.
Pearl-For some reason, Giratina was reasonably harder here, simply because I fought it with all level 90s. Caught it on my second try with a Quick Ball.
Platinum-Oh, this Giratina was WAY harder than the last two. I chose Torterra on here, and most of my Pokemon were ground types, so levitate killed me. Caught it on my 21st try with a Timer Ball.
HGSS-I can't read Japanese, but it was still easy to get. I was in the Shinto Ruins or something (Serebii.net gives good translating!) and I picked Giratina.
I have the Arceus for the English version on my Diamond, so I may pick Giratina tomorrow. (:D :D :D :D HGSS OUT TOMMOWOW IN ENGWISH!) (That means: HeartGold and SoulSilver out tomorrow in english!!!!!!!!!!!!!!!!!!!!!!!!)