Its like this for everyone... either Fire or Water, no-one ever chooses Grass, but heres what happens to the poor Grass type...
Prof. Oak:"OK Ash, you chose Charmander! Gary, what will you pick?
Gary: "Hmm... I'll choose... Squirtle!
Prof. Oak:"Alright, well I've got some buisness to take care of, You boys go fill that Pokedex now!"
Prof. Oak:"*sigh* Bulbasaur again?"
So, Prof. Oak takes Bulbasaur to the back off the lab where the room filled with dead pokemon are, he places Bulbasaur on the table...
Prof. Oak:"Sorry, old friend..."
Bulbasaur:" Bulbasaur! Bulbasau... Bulba..."
- as Bulbasaur's vision slowly fades to black, the last thing he sees is Prof. Oak's red eyes*
This is what will happen to EVERY unchosen Pokemon, dont let anymore Pokemon be unchosen, just... dont...