>>58947954I decided to check out pre-League Gen II as it was originally designed
>Gold (Japanese, so no Route 46 Jigglypuff, no Celebi, Odd Egg, Pokéwalker, Safari Zone, etc.)>No trading with other games for version-exclusives, trade evolutions, etc.>No Time Capsule trades to fill out the missing original 151>No Mystery Gift (ie. no Stones outside of recurring Sun Stones and two Moon Stones before post-game)>No glitches (ie. no cloning glitch)>Went with Cyndaquil line, so no Chikorita or Totodile lines>Breeding is allowed, so you can get both Espeon and UmbreonAt the final count, it's 161/251 Pokémon pre-League. If you go up to the second credits, you can reach 199/251, meaning 38 Pokémon are post-game.
By comparison, if you were playing Red under similar conditions, it's 123/151 Pokémon pre-League, and 1 more post-game (Mewtwo) for a total of 124.
Looking at Diamond under similar conditions, it's 130/151 pre-League, but 357/493 post-game, that's an additional 227 Pokémon that become available even without GBA cartridges, trading, Ranger, events, etc.