The subpages linked here detail some numbers and requirements linked to completing the Pokédex in each of Red, Green, Blue, or Yellow.
The ultimate goal of the Professor Oak Challenge.
In Mystery Dungeon, I often strive to recruit as many Pokémon as possible at the evolutionary stage I want them at, no matter their spawn rate, and evolve only the ones I can't get otherwise. These pages outline what Pokémon can be obtained with a similar approach to Red, Green, Blue, and Yellow.