Hoooo boy, I got all box Legendaries from Gen II to Gen IV as Shinies (Lugia, Ho-Oh, Kyogre, Groudon, and Rayquaza. I already had Dialga, Palkia, and Giratina through the GameStop promotion along with the Legendary Dogs) through trades in GTS. But there's this nagging feeling that's telling me those were hacked Pokemon because the OTs look a bit implausible (0001337 for example)... Oh well! I like having these uber trophies anyway.
I should try to target Shiny Latios and Shiny Latias next.