We have Complete Pokédex, but what about Complete Pokédex in Two Games? (One game played on the Ruby field and one played on the Sapphire field). I'm still far from an expert on this game (honestly I'm still working on completing the Pokédex untimed/playing through the game to learn more with experience), but would that be possible to complete the Pokédex in only two games, assuming someone can of course survive long enough to catch em all?

Could be possible, but I don't think it would be really interesting. One of my first catch'em all run was with no game over, but at the end I still reseted the game to target some missing pokemons. So it would just be the same run with less option and the frustration to lose a full run from small mistakes leading to a game over instead of a couple of minutes of time lose.