My vote goes to Charizard simply because I've had the most fun with this guy. When I first started playing the games (back with Pokemon Blue) I chose a Charmander, raised it and eventually turned it into a powerful Charizard. Even when I started watching the animé, I realized that Charmander was my favourite Pokemon, and even as a Charmeleon who was disobedient to Ash, I still thought it's rebellious form was very unique.
So, yeah, Charizard wins because of it's superior design, it's power in the games and, in the animé, it's striking personality that can be described as none other than "cool".