Hmm...flying, fire, dragon, ghost types...I love those, and more. I can't really choose a favorite, because I love so many...
However, I will explain my reasons for these types.
Fire: My very first Pokemon was Infernape, a fire type. Fire types usually have great designs, and represent the fire in my spirit.
Flying: Almost all of them have a natural beauty about them, and usually excel in speed and attack, two of my favorite stats, besides special attack.
Ghost: They are very mysterious, and have surprising abilities. Not only that, many of them have a wicked design, and just generally cool.
Dragon: Perhaps the strongest type, possessing phenomenal stats, and have a mystic feel to them, especially Altaria and Dragonair...and because they are just boss in general. XD