I would have picked Entei, but I personally like Lugia better.

Lugia for the win because if it got into a fight with any of the otherchoices, it would OWN THEM ALL with Psychic, then an AEROBLAST. Sorry Ho-oh, but I thought you were less creative than Lugia.

I personally liked Suicune, then Celebi, and then Lugia. Suicune was just by far the coolest (not to mention I played Crystal first out of the three). It was so graceful, it was a TANK, and I still love how we can't really say what it is? A cheetah? A wolf? A dog?
Celebi was cool because practically nobody knew it existed, since Nintendo never made the Celebi event for us Americans (grrr...) and it was cute, green, and controlled time.
Of course, everyone loves Lugia. Its kinda tragic, how it has to stay hidden either because a maniac is trying to harness its power to destroy the world, or its power destroys the world. Anyways, the anime Aeroblast animation was epic.
Ho-oh, I guess, but Sacred Fire made it so hard to catch. God! Why do you have to keep burning me? Plus, Crystal Ho-oh doesn't even have Sacred Fire, which is just depressing.
Raikou's Gold and Silver sprite was just scary. End of story.
I didn't like Entei because its backsprite is still scary, so using it is just weird. Ok. End of rant.