[Mika]

They resemble dragons, but they aren't dragons. They aren't dragon types, and they don't have the stats. MOST dragons are pseudolegendaries. Salamence and Dragonite for example.

Lance has three Dragonites. The only reason he had gyarados and aerodactyl is because in the original 150? There's only one dragon type, and that's the dratini line. No other pokemon from the 150 originals is a true dragon. Gyarados could learn dragon moves, but only pokemon with dragon types are true dragons.