>>56419505Gym leaders are an extremely small percentage of battles. Most of the time between route/dungeon trainers and wild pokemon you're running up against stuff that bulbasaur sucks at, especially with only grass and normal type moves at your disposal. Using <1% of the game as an argument as to why it's good is just sad. It's Kanto. Birds, bugs, poison types, grass types everywhere especially on trainer routes.
You say "with ease" after listing toxic, rest, and leech seed as your strategy. What is that easy in comparison to exactly? Obviously not the other starters. Hell, almost all other pokemon in the game will give you an easier time in the average battle. It's fine in later games after they actually give it moves, but in RBY it is a bad pokemon on the objective level, and I'm not remotely convinced you or anyone really runs those four moves you listed in a run of gen 1, and if they did they better love 5+ minute repetitive battles.