Generation I is the ur-text: 150 creatures (151 once you count the Mew hidden in the code), a fifteen-type chart with no Dark or Steel yet invented to keep Psychic in check, and the Red and Blue cartridges that turned a Game Boy link cable into a piece of social technology. Every Pokedex since is a sequel to this one.
The games and the cartoon never quite agreed, and that gap is where the fun lives. On screen, Pikachu refused its Poke Ball and rode on a shoulder instead; Charmander arrived with a sob story; Team Rocket kept failing upward week after week. A creature the games treated as a stat line became, in the show, a personality with a backstory and an owner.
Gen I was also gloriously broken, and knowing the era means knowing its seams. A Ghost move couldn't touch a Psychic despite what the type chart promised, so Psychics ran the whole metagame. Hyper Beam skipped its recharge turn if it knocked the target out. And a corrupted encounter called MissingNo would happily clone the sixth item in your bag, usually a stack of Rare Candies.