Is there a complete database of Pokémon data?
Can't vouch for its completeness, but http://www.pokemon.com/us/pokemon-trading-card-game/database/ seems to be a similar resource to the Magic TCG's "Gatherer".  

Certainly when I made a request for cards with the name "Pikachu" I got 27 card results, so it seems like it could keep a deckbuilder busy for quite a while...