Sad to say that Kingdra is probably the only Dragon worth training. Their status are superior indeed, tch, but all evolved Dragons except Kingdra have a 2x weakness to ice due to their typing. If you're planning to use Dragons for link battles good strategies are out there. However, their double ice weakness makes them more vulnerable to OHKOs than most pokemon, and with ice moves themselves being one of the best weakness exploiters because so many types are weak to ice, the opponent is bound to have a pokemon with an ice move. With double weakness STAB doesn't even matter, the damage is simply too great.
Best Dragons to train would be Rayquaza, Salamence, Dragonite, and Kingdra. Best uses for a Dragon? Sweeper, though I don't know about Kingdra... Altaria is fast to raise, needs only 600000EXP. pts., Perish Song offers room for some strategy, Sky Attack though a 2-turn move is respectable, with high-criticality and a chance to flinch the opponent, also great self-healer.