Its pretty chicken shit that every legendary has their own unique niche or abilities with the except of the kanto trio. Zapdos is only been where he's been because of great typing to compliment his stats, but his movepool like the other 2 is still pretty shallow.

Lets say they each got a unique ability.

>Moltres
>Ability: Endless heat
Makes any move that requires charging or recharge only last 1 turn. Essentially it always has a power herb.

>Articuno:
>Ability: Coldfront
33.3% boost to all ice type moves on the field. Grants user immunity to ice type moves and burn.

>Zapdos
> Overcharge
Being hit with an electric type move increases this pokemon's special defense 1 state. Doesn't cancel damage.

Birds fixed now?