Lets see(skills only from lvling):
[highlight=red]Charizard counter 8 types: grass, bugs, steel, ice, dragon, fight, ghost, psychic(Shadow Claw, Dragon Claw, Flare Blitz, Wing Attack).[/highlight]
[highlight=blue]Blastoise counter 6 types: fire, ice, rock, ground, ghost, psychic(Hydropump, Flash Cannon, Bite, Skull Bash).[/highlight]
[highlight=green]Venusaur counter 5 types: bug, grass, ground, rock, water(Poison Powder, Solar Beam, Double Edge, any random of his skills).[/highlight]
Probably thats why charmander is the best choise, because we have harder start and easier late game.
In each generation fire pokemon have better move set from lvling.