Pokémon tcg was one of the very few games I had for the system, I played that thing to pieces! I loved making all sorts of decks (usually a mono deck) and using them against everything. I definitely recommend playing Pokémon tcg 2, there's a lot more battles to be had and a lot more than just "gyms+e4" format.
I didn't really have a standout deck in the first game, but the second one I recall a insanely powerful one I made around Dark Raichu, Dark Cleffable, and GR Mewtwo. GR Mewtwo had an ability to boost the power of Dark Pokémon moves by either 0, 10, or 20, but unlike similar abilities, it affected bench damage too. Both Raichu and Cleffable had coin flips, but they pretty much always was OP, hitting the active Pokémon for a good chunk of damage, and dealing up to 40 damage to EACH bench Pokémon for Raichu, and bench damage + sleep for Cleffable, KOing things almost each time. Cleffable also had the same thing GR Mewtwo had but to reduce damage for Dark Pokémon instead. I had Kangaskon to wall and draw cards, Dodrio to give free retreats to almost everything, and Dark Dragoneir/Dragonite to get the Pokémon out on the field to round up the rest of the Pokémon I used (they all hit hard too if needed).
P.S. Forgive me for any misspelling of Pokémon names I may have done.