Charizard, Milotic, and Gyarados may look like dragons, but they aren't dragon pokemon.
I'd say Rayquaza.
I have to explain something to all of you right now just cause it doesn't say it directly does not mean anything. All the guys that I put up there actually are dragons. Pokemon are also determined by egg groups. All of them are so please get your facts straight before you say that someone else is wrong.
See, it's just that I've heard a lot of people say that Charizard, Gyarados should be Dragon type, etc.
If you're talking about egg groups, then can I count Treecko, Grovyle, and Sceptile as "dragons" too?
WHAAAAAAAAT?!!! Salamence aint on the list and Aerodactyl is while he isn't even a Dragon type? Whoa... But Salamence certainly is my favorite, along with Latios.