1st gen: Articuno
I mean, come on! Articuno! Flying ice sparks, spectacular head and tail design, tremendous wingspan, and he had no trouble altogether avoiding the projectiles that collector guy in Pokémon 2000 kept hurling at him. He evaded all the projectiles and came very closer to the airship. If memory serves, he was also the first to land a hit on Lugia. And of course he was the first to faint, after all he was tired, having to fend off Lugia, the airship and his brothers all alone and by himself! Oh and of course, Noland's Friendly Neighbour Articuno is simply spectacular in battle.
2nd gen: Celebi... It is small, cute, can travel in time, it goes straight on to the notion of legendary... did I mention it's cute? Its feet and wings give it some kind of charm.
3rd gen: Rayquaza... despite the fact I don't know it that much, I certainly prefer it to th others. Looks great in the movie, and its status in legend as the mediator between the other creatures (Kyogre/Groudon). I likes very much that its behaviour and design, for being a "Dragon" type, is more resemblant of the eastern (chinese, serpent-like) concept of the dragon than it is to the western (european, lizard-like).
4th gen: undecided, and by their looks frankly I don't care. The triplet of little angels or fairies or whatever looks very nice and huggable, however.
