hmm
good reasoning chanseymaster....
but if i'm correct: ash always yells :woow A....(fill in name of Pokémon...)
so if we have to believe him, there would be no unique legendary...
he also sais this if he sees ho-oh for the second time, he sais it when articuno flies before him, saving him and todd from falling in a whole (somewhere in the series)
he sais a lugia (this has been proven to us) and he probably also said: woow, a lucario or something like that...
he only didn't say it when facing mew and mewtwo...in the first movie and second time he saw mewtwo, he didn't say it...
so if we believe him, no legendary except mew and mewtwo is unique...
greets,
the psychotrainer....