Yea, it's completely random. After waking them in the burnt out tower place i caught Raikou pretty much straight away, before i'd even got Suicune. It was a complete fluke with a great ball lol.
Dude this sounds impossible but i found all three of them in a row and caught them all with a pokeball it took me 1 try each it was so cool im getting really crazy because i found them again at kanto i think im crazy but i caught them
i have 1 more thing i need help with. can u find a scyther in this game? ive checked everywhere and i cant find anything.
Yes, as pisces said you can catch it in the bug contest which is held in the grass area (national park) above golderrod city. You can also catch a pinsir if you like it. P.S. I can't remember if the contest is organized everyday or some days of the week.
The bug catching contest is held every Tuesday, Thursday and Saturday.