Dorkly did a poll, and people voted. Here are the top 25:
Haunter
Snorlax
Suicune
Articuno
Metagross
Zapdos
Scyther
Umbreon
Entei
Scizor
Blaziken
Tyranitar
Gyarados
Lucario
Alakazam
Typhlosion
Rayquaza
Dragonite
Arcanine
Lugia
Gengar
Mew
Blastoise
Mewtwo
And Number One was...
Who else but good ol' Charizard?
The full results here.
Haunter
Snorlax
Suicune
Articuno
Metagross
Zapdos
Scyther
Umbreon
Entei
Scizor
Blaziken
Tyranitar
Gyarados
Lucario
Alakazam
Typhlosion
Rayquaza
Dragonite
Arcanine
Lugia
Gengar
Mew
Blastoise
Mewtwo
And Number One was...
Who else but good ol' Charizard?
The full results here.