I will tell you how to get the shiny legendary on G/S/C R/S/E and D/P/P
ITs really easy actually for R/S/E and D/P/P to get the shiny. ALl you do really is save in front of the legendary pkmn and keep talking to it and restarting until its shiny. So if you save in front of Giratina, you just talk to it and if its not shiny, turn off your ds and try again. It took me about 4 days for each legendary to become shiny.
If you still have G/S/C then theres a litte extra to do for the legendary dogs. If your hunting for them, but you HAVE NOT seen them yet, then save before you go into any wild pkmn map. If your lucky enough to save before you encounter one, then its the same process. You simply turn off your game, turn it back on, and keep encountering it until its shiny
KEEP IN MIND!! With the legendary dogs, if you have already seen it and it wsnt shiny, then it will nnever be shiny for you. you MUST see it as a shiny the FIRST time you see it!
Hope this helps people who really want the shiny legnedary pkmn!