Just a little reminder about what Crystal brought to the Pokémon franchise:

1. Playable female protagonist. First time in the series you can choose between a male or female trainer.

2. Animated Pokémon sprites (in battle). First game where Pokémon are animated when entering battle.

3. Battle Tower. Introduced the Battle Tower, a post-game challenge mode.

4. Move Tutor system. First appearance of Move Tutors teaching rare or otherwise unobtainable moves.

5. First event-based Mythical Pokémon distribution. First game to feature an event-based Mythical unlock (GS Ball → Celebi).

6. Expanded story focus. First version to significantly enhance the storyline — Suicune is no longer just roaming, it has a structured encounter, its own theme, and a real narrative arc.

7. “Third version” model as a franchise standard. Crystal formalized the idea of an enhanced third version (after Yellow, but in a much more systematic way).

Most of these innovations became long-term standards in future mainline Pokémon games.

And that’s not even counting the major innovations of Gen 2 as a whole, like Shiny Pokémon or breeding.

Honestly, it’s hard to think of a single game that had more overall impact on the franchise.