I've seen exactly one legit shiny. It was a safari zone eggsecute in firered, which I managed to catch, thus using up all my shiny luck for the next two generations. At least, that's my theory. Seriously, I couldn't even chain past 10 in gen 4.
IT'S SUPERMAN! IT'S SPIDER-MAN! IT'S — S***, IS IT MERCER?! IT'S... not clawing our arms off, it must be on our side!