Originally Posted by Calypso
None of the legendary trios are ever regarded as Uber in any generation. Infact, even in RBY, Moltres and Articuno were only BL, and Zapdos has always been OU. But the reason the former two are relatively unseen competitively is due to the prevalance of Stealth Rock, which seriously hampers their use, considering the 50% health loss every time they switch in. Articuno also has a terrible typing, especially since it focuses on the defensive spectrum. None are bad Pokemon in any sense, they just can't perform particularly well in the Uber environment.
This information isnt completely correct. Zapdos was uu in the pervious generations but is uu in the 5th gen. Moltres was UU in the 4th gen.