Oh, so many! ~♪
May I list my nominations and then my final choice? (and go into Ruby-mode in order to do so?)
Dragonair - Its beauty is wonderful, with its flowing blue body, such grace! The pearls at its neck and tail simply radiate expense, beauty, sophistication! Within a family that ranges from cute to powerful, Dragonair holds the beauty with its divine appearance.
Milotic - Oh, so pretty! ♥ The only Pokémon that grows through beauty, surely it should hold a place here? Its streamlined body is glorious to behold, and its technicoloured fan-tail shows off its elegance. Its long streamers may flow with grace as it moves, showing the true beauty of this Pokémon!
Articuno - How much grace can one bird hold? With its sparkling appendages and glistening wings, surely the icy, shimmering glory of this Pokémon holds a place on this list? The way it glides on the winds and glitters with ice makes its beauty shine on through any light!
Ninetales - Ah, dear Ninetales! So graceful, firey and yet icy in demeanour; its sleek body is held so wonderfully, the ruff of fur on its neck so soft and fluffy, while its tails flow out behind it in such a wonderful way! If any is deserving of the crown, Ninetales is.
But I'm afraid my vote goes to a less obvious creature... the modest Misdreavus.
Why? It's simply adorable! Those smooth curves in its body, the contrast of violet and pink, the sly grin and that shining necklace of red make Misdreavus the most beautiful of all in my humble opinion!