>>40160710So, I've gone through each and every canon game, and listed out how many of each legendary appears. The first number is how many appear in the GBA-DS games, and the second is how many appear in the 3DS-Switch games, not including times they're explicitly from another universe.
>Birds: 6+, 3+>Mewtwo: 5+, 2+>Mew: 3+>Beasts: 7+, 1+>Tower: 4+>Celebi: 2+>Regis: 4+, 2+>Latis: 5+, 2+>Weather: 3+, 1+>Jirachi: 0+, 1+>Deoxys: 3+, 1+>Lake: 2+>Creation: 2+, 1?+>Cresselia: 5+>Heatran: 4+>Regigigas: 5+, 1+>Manaphy: 3+>Darkrai: 2+>Shaymin: 2+>Arceus: 1+>Victini: 1+>Musketeer: 2+, 1+>Kami: 2+, 1+1?+>Tao: 1+>XY: 1+>Zygarde: Many>Hoopa: 1+>Silvally: 3>Tapus: 1+>Cosmog: Many>UBs: Many>Necrozma: 1+>Meltan/Melmetal: Many>Meloetta, Keldeo, Genesect, Diancie, Volcanion, Magearna, Marshadow, Zeraora: UnclearThe decrease in appearances for legendaries from Gen 5 onward is almost entirely due to lack of canon side games, though, so how many Victinis or Yveltals there actually are is unclear, but I entirely doubt any pokemon on this list, other than the ones I mentioned here
>>40165528 are actually unique in any way.