I'd say late 90s because the Pokémon franchise absolutely dominated.
I got a gameboy color only so that I could play pokemon red (and later yellow & gold). Then I got a gameboy advance only to play pokemon sapphire.
When I watched TV, I watched the first season of Pokémon.
During school breaks everyone played with and talked about Pokémon cards.
The first 2 movies (1998-2000) were huge.
I even got a pikachu doll.