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What gen 2 gave us.
>Pokérus
>Breeding and Egg moves
>Shiny Pokemon (debatable relevance)
>Special split
>Weather
>Day and Night
>Happiness
>Roar and Whirlwind's in-battle effect
>Berries
>Steel and Edgy-types
>Freeze can be naturally cured
>Genders
>muh two regions
>Hold Items
>Hidden Power
>Battle Tower (mother of future facilities/frontiers/subway
>First Move Tutors (Game Corner and Stadium 2)
>Entry Hazards
>Skarmory (Contrary to popular belief, Skarmory was not introduced in Gen 3).
What gen 3 gave us.
>IVs
>EVs
>Natures
>Abilities
>Double Battles
>EV Berries
>Mini games (contests, bases)
>No backwards compatibility
So, whether you like it or not, Gen 2 introduced far more things than Gen 3. Furthermore, EVs and IVs technically existed since Gen 1 (with a different name and formula, but still).