Kyurem. looks good in Normal Forme, but even cooler (get it? cause hes an Ice Type?) in Black and White Formes.
Found it really difficult to choose between Lugia and Ho-Oh as my favourite legendary from the choices above as I really like both of their designs and their respective signature moves, aeroblast and sacred fire. Decided to go with Lugia in the end;
Dialga. A dragon that wears steel armor and controls time with its roars and heartbeat. Can't get much cooler than that.
"N's heart is pure and innocent. But there is nothing more beautiful and terrifying than innocence." ---Concordia
I love a lot of mighty legendaries, such as Lugia, Ho-oh, Rayquaza, Arceus, and Kyurem. I like these in particular because while they have elegant designs, they remain a force to be reckoned with. For nostalgic reasons, my top favorite would be Ho-oh. I adore the different colored feathers and its location, as well as its background story. I also had Gold Version, after all.
Groudon now has one vote XDD
He was really really helpful. Drought + Solarbeam literally drains the energy out of water pokemons, not to mention Fire Blast gets a huge plus as well XDD It's more the ability that was highly useful to me when I used him in Ruby against Steven because my Blaziken and Castform both got huge advsntages...XDD
I still like Ho-oh the best because it always seemed so powerful since it can resurect dead Pokemon. It is also the most mysterious in a way since Ash has seen in from a distance several times but never got to meet it even though he has met the majority of Legendary Pokemon.
Ho-oh. I liked the design and the description of it.
Have to go with the Original. Mewtwo was the first great legendary. Not to say there aren't those who match him in later generations I have a favorite legendary in every gen I've played. Nostalgia is king however and so the Psionic Sentience gets my vote.