Why Johto is underrated.
Imagine playing Pokemon RBY and now you get to play Johto.
You are greeted in this new region. First thing you notice is the night and day change and the importance of time.

After you reach the first town you can explore dungeons with puzzles and if successfully solved grant you nice items.

Now you are on your way on the second gym leader and you hear about some strange creature that makes sounds in the dark cave every friday. You realise that this game also introduces timed events.

Furthermore you can keep in touch with trainers and when rematching them their team also gets stronger not only that they give you important information on when and where to encounter rare Pokemons. The quest for dialogue and self discovery is beautiful in this game and shows how a proper rpg should be.

Even after beating the game you think it is over BUT no you can actually take a BOAT and explore the previous region.

Even after defeating every Kanto gym leader you think it's finally over BUT NO in the top of that mountain is the true boss of the game all along.

No forced legendary encounter. You have to explore the dungeons of Lugia and HoHo at your own pace and will.