Personally, I rank Ho-oh and Lugia about the same in terms of shininess. And Entei, Suicune, and Raikou are clearly better shinies than Lugia and Ho-oh, too. But the best shinies of Johto are mostly non-legendaries. Shinies like Tyranitar, Scizor, Houndoom, Espeon, and Miltank...and there are others that I can't remember at the moment, but they're certainly the best in my eyes.