>>35089176The games have, relative to the games that came after, an unparalleled sense of exploration. The GB games don't push the players into any plot, it lets them breathe and gives them the opportunity to just explore a route or cave, catch some Pokémon and fight some trainers. They only occasionally throw in a recurring NPC like your rival or the Rockets, the former being an important benchmarks and the latter being a small-starting but steadily-increasing threat that culminates in one big, singular event for each game (as opposed to later games where they hijack the plot early and keep it that way until nearly the end). Later games focus on narrative over exploration and ultimately become, in my opinion, boring and railroady.
The GB games are far from perfect, the balance is off and they have numerous glitches, especially in Gen 1, but I think they're the best despite those simply because of their core game design. For all the balance improvements and glitch-free gameplay of Gen 6 and 7, it bores me to tears.