Re: Pokémon Sun and Moon (Please put leaks and spoilers in spoil boxes!)
Actually I went through all the encounter rates and took a look at the alolan pokedex order (+what islands they're found on) to figure out what old pokemon may be exclusives. All of these are guesses, though some are really obvious and some aren't. I'll put a note if it's possible I don't know what the fuck I'm thinking. The (Sun) ones don't show up at all in Pokemon Moon's encounter rates btw.
Actually I went through all the encounter rates and took a look at the alolan pokedex order (+what islands they're found on) to figure out what old pokemon may be exclusives. All of these are guesses, though some are really obvious and some aren't. I'll put a note if it's possible I don't know what the fuck I'm thinking. The (Sun) ones don't show up at all in Pokemon Moon's encounter rates btw.
Cottonee/Whimsicott (Sun) / Petilil/Lilligant (Moon)
Rufflet/Braviary (Sun) / Vullaby/Mandibuzz (Moon)
**Note: There's actually encounter rates for both evolved Lycanroc forms in Moon on a later island (during daytime and nighttime), so it's possible they might not even be version exclusive.
Passimian (Sun) / Oranguru (Moon)
Turtonator (Sun) / Torkoal (Moon?) OR Drampa (Moon) **Turtonator is found in the exact same place and level as Torkoal but it's possible it could be a pair with Drampa since Drampa doesn't appear to have a pair in its location. Either way, Turtonator is (Sun), Drampa is (Moon), Torkoal is at least in Moon.
Alolan Vulpix/Ninetales (Sun) / Alolan Sandshrew/Sandslash (Moon)
Gible/Gabite/Garchomp (Sun) / Trapinch/Vibrava/Flygon (Moon)
Castform, Goomy and Vannilite don't have encounter rates, and none of them really have another pokemon close to them in the pokedex to pair them with. Vannilite could be a pair with Sneasel or Snorunt, but I can't really make that call. Could even be a pair with Drampa. Castform could be a gift. No fucking idea about Goomy.
Porygon also isn't catchable, I considered that it might be a pair with Beldum but it honestly could just be a gift pokemon. I also really don't want Beldum to be Moon exclusive because I really want to use it.
and then there's the known ones like the cover legendaries. some of the available fossils may be exclusives like they did with fossils in earlier games.
there's also the chance that you can get an exclusive through in-game trade kinda like cottonee/petilil in b/w.
Rufflet/Braviary (Sun) / Vullaby/Mandibuzz (Moon)
**Note: There's actually encounter rates for both evolved Lycanroc forms in Moon on a later island (during daytime and nighttime), so it's possible they might not even be version exclusive.
Passimian (Sun) / Oranguru (Moon)
Turtonator (Sun) / Torkoal (Moon?) OR Drampa (Moon) **Turtonator is found in the exact same place and level as Torkoal but it's possible it could be a pair with Drampa since Drampa doesn't appear to have a pair in its location. Either way, Turtonator is (Sun), Drampa is (Moon), Torkoal is at least in Moon.
Alolan Vulpix/Ninetales (Sun) / Alolan Sandshrew/Sandslash (Moon)
Gible/Gabite/Garchomp (Sun) / Trapinch/Vibrava/Flygon (Moon)
Castform, Goomy and Vannilite don't have encounter rates, and none of them really have another pokemon close to them in the pokedex to pair them with. Vannilite could be a pair with Sneasel or Snorunt, but I can't really make that call. Could even be a pair with Drampa. Castform could be a gift. No fucking idea about Goomy.
Porygon also isn't catchable, I considered that it might be a pair with Beldum but it honestly could just be a gift pokemon. I also really don't want Beldum to be Moon exclusive because I really want to use it.
and then there's the known ones like the cover legendaries. some of the available fossils may be exclusives like they did with fossils in earlier games.
there's also the chance that you can get an exclusive through in-game trade kinda like cottonee/petilil in b/w.